THE EFFECT OF CHANGES IN TORT LAWS ON CESAREAN SECTION RATES IN THE UNITED STATES
by ALLISON JEAN TAYLOR
BEVERLY A. MULVIHILL, COMMITTEE CHAIR MEREDITH L. KILGORE MICHAEL A. MORRISEY LEONARD J. NELSON III
MARTHA SLAY WINGATE
A DISSERTATION
Submitted to the graduate faculty of The University of Alabama at Birmingham, in partial fulfillment of the requirements for the degree of
Doctor of Public Health
BIRMINGHAM, ALABAMA
2011
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THE EFFECT OF CHANGES IN TORT LAWS ON CESAREAN SECTION RATES IN THE UNITED STATES
ALLISON JEAN TAYLOR
MATERNAL AND CHILD HEALTH
ABSTRACT
“Defensive medicine”, medical practice decisions based on fear of malpractice
litigation and where risks may outweigh health and cost benefits, is a proposed
contributor to increasing cesarean rates in the U.S. Some studies suggest that changes in
laws governing medical malpractice actions may decrease the cesarean rate by relieving
pressures driving defensive medicine.
This study examined whether, in states that have adopted certain tort reform
measures, the probability of having a cesarean delivery is lower following
implementation of the reform measures. A database of state legislation and court
decisions and National Center for Health Statistics natality data files (1991-2004) were
used to model state and year fixed effects. Tort laws were grouped as those directly
affecting recovery in a legal action (non-economic damages caps, collateral source offset)
and those with an indirect effect (contingency fees limits, periodic payments, joint and
several liability rule, statutes of limitations, statutes of repose) and examined separately
as individual reforms. The analysis was limited to live singleton births and adjusted for
maternal age, race, education, marital status, diabetes, hypertension, tobacco use, pre-
natal care utilization, gestational age, birthweight, and non-vertex presentation.
Coefficients ranged from -0.01-0.03 for individual tort reforms. The effect was
slightly greater for direct than for indirect tort reforms, -0.009 compared to -0.004. Non-
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economic damages caps were associated with a small reduction in cesarean rates, with a
slightly greater effect shown for collateral source laws and statutes of limitations.
The findings may indicate that there is little effect of tort reform on defensive
medicine, for which cesarean was a marker. It is also possible that the minimal effect
observed is due to small numbers of tort law changes during the study period or that
unobserved time-varying factors influencing the decision to perform cesarean delivery
exerted a greater effect than tort reform. Based on findings of this study and several
others, tort reforms alone are likely insufficient to reduce defensive medicine. If tort
reforms do not contribute to reduction in cesarean rates, attention must be focused on
other approaches to influence clinical practice patterns and to achieve rate reduction
goals.
Keywords: tort reform, defensive medicine, cesarean, obstetric
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DEDICATION To my late father, Lincoln H. Taylor, Jr. The knowledge that it was very important to him that I complete this degree fueled my determination when I might otherwise have been inclined to consider abandoning this endeavor.
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ACKNOWLEDGMENTS
I acknowledge the following persons for their assistance and guidance:
My committee chair, Dr. Beverly A. Mulvihill, and committee members, Dr. Michael A. Morrisey, Dr. Meredith L. Kilgore, Dr. Martha Slay Wingate, and Leonard J. Nelson III.
Dr. Donna Petersen and the late Dr. Greg Alexander for recruiting me to the Department of Maternal and Child Health and encouraging my research interests.
Steven Kazan, Esq., former boss and renowned trial lawyer, for whom I worked as a paralegal on medical negligence cases in Oakland, California for ten years.
Dr. Elizabeth Delzell, Dr. Philip Cole, and Dr. Gerald McGwin, UAB Department of Epidemiology, for their long-time mentorship.
My sister, Amy T. Fleury, for her wise counsel with respect to balancing priorities.
My parents, Lincoln H. Taylor, Jr. and Nancy B. Taylor, who instilled in me an appreciation for scientific thought and the value of education.
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TABLE OF CONTENTS
ABSTRACT……………….….…..…………………………………………………... iii
DEDICATION…………….…….……….……………………………………………. v
ACKNOWLEDGMENTS….…….…………………….……………………………… vi
LIST OF TABLES…………….….………………………………………….………… ix
LIST OF FIGURES……………….…………………………………………………… x
CHAPTER
1 INTRODUCTION……………..…………………..………..……………………….…1
2 BACKGROUND……..……………………………….………………………..………3
History of Cesarean Section ...................................................................................... 3 Increasing Cesarean Section Rates ............................................................................ 5 Risks of Cesarean versus Vaginal Delivery ............................................................... 7 Clinical Indications for Cesarean Delivery .............................................................. 11 Liability Pressure and Defensive Medicine ............................................................. 19 Literature on Tort Reform and Defensive Medicine ................................................ 28 Literature on Defensive Medicine in Obstetrics ....................................................... 35 Gaps in the Literature.............................................................................................. 37
3 METHODS ............................................................................................................... 44
Conceptual Framework ........................................................................................... 44 Research Questions ................................................................................................. 45 Subjects .................................................................................................................. 46 Geographic Units of Analysis ................................................................................. 46 Data Sets................................................................................................................. 46 Births ................................................................................................................. 46 Tort Reform ....................................................................................................... 47 Variables ................................................................................................................ 48 Dependent Variable............................................................................................ 48 Independent Variables ........................................................................................ 49 Confounders ........................................................................................................... 53 Maternal Demographic Characteristics ............................................................... 54 Maternal Medical History .................................................................................. 57
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Labor and Delivery Characteristics ...................................................................... 60 Infant Characteristics ........................................................................................... 61 Excluded Variables ................................................................................................... 63 Unmeasured Confounders ......................................................................................... 74 Tort Reform Analysis ............................................................................................... 76 Fixed Effects Modeling ........................................................................................ 76 Omitted Variable Bias and Endogeneity ............................................................... 77
4 RESULTS ................................................................................................................. 80
Descriptive Analyses............................................................................................ 80 Fixed Effects Analysis ......................................................................................... 89 5 CONCLUSIONS ...................................................................................................... 94
Strengths ............................................................................................................... 96 Limitations............................................................................................................ 96 Implications .......................................................................................................... 99
REFERENCES ............................................................................................................ 103
APPENDIX A: INSTITUTIONAL REVIEW BOARD APPROVAL FORM……..…112
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LIST OF TABLES
Table
1 Percent of Reported Pregnancy and Labor and Delivery Complications, U.S. Standard Certificate of Live Birth (1989 Revision), 1991-2002 ............................. 13 2 Key Defensive Medicine Literature............................................................................ 40 3 Variables Considered for Inclusion the Fixed Effects Models ..................................... 69 4 Variables Included in Descriptive and/or Econometric Analyses ................................ 70 5. Missing Values for Variables Included in Econometric Analyses ............................... 73 6 Numbers of Live Singleton Births Per Year, United States, 1991-2004 ...................... 79 . 7 Live Singleton Births by Delivery Method, United States, 1991-2004 ........................ 81 8 Cesarean Deliveries (Live Singleton Births) by State, Ordered by Rate, United States, 1991-2004 ............................................................................................... 82 9 Number of States with Tort Reforms in Effect by Year, 1991-2004 ........................... 84 10 Maternal Characteristics by Delivery Method, Live Singleton Births, United States, 1991-2004 ............................................................................................... 85 11 Infant Characteristics by Delivery Method, Live Singleton Births, United States, 1991-2004 ............................................................................................... 86 12 Cesarean Deliveries (Live Singleton Births) by State, 1991 and 2004 ..................... 87 13 Parameter Estimates for the Effect of Direct and Indirect Tort Reforms on Cesarean Delivery ..................................................................................................... 91 14 Alternative Model Specifications ............................................................................. 92 15 Parameter Estimates, Effect of Tort Reforms on Cesarean Delivery by Race ............ 93 16 Regression Coefficients, Effect of Tort Reforms on Cesarean Delivery by Maternal Educational Attainment and Marital Status ..................................................... 93
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LIST OF FIGURES
Figure Page 1 Relationship Among Several Branches of Tort Reform Literature .............................. 29
2 Percent of Cesarean Deliveries Among Live Singleton Births, United States, 1991-2004 ..................................................................................................................... 88
1
CHAPTER 1
INTRODUCTION
Cesarean section is the surgical delivery of an infant, a procedure once used solely
for emergencies threatening the life of the mother but more recently used to reduce the
likelihood of injury or death of either mother or infant. Cesarean rates have grown
dramatically over the past forty years, from 5.5 per 100 live births in 1970 (1) to 32.9 per
100 in 2009, (2) which has caused concern that infants may be sometimes delivered
surgically in cases where risks outweigh benefits in terms of both health and cost.
“Defensive medicine,” medical practice decisions based on fear of malpractice litigation,
has been posited as a contributor to this increase. Some studies (described in Chapter 2)
suggest that changes in certain laws governing medical malpractice actions may
contribute to decreasing the cesarean rate by relieving some of the pressures that drive
defensive medicine, but this question has not been fully resolved by empirical research.
Tort reform has received considerable media and legislative attention in recent
years, with physicians arguing in favor of reform and trial lawyers arguing against it. Tort
reform legislation is often proposed in response to a perceived “malpractice crisis”,
characterized by increasing malpractice insurance premiums or decreasing numbers of
malpractice insurance carriers. The debate on defensive medicine often centers on a
perceived contribution to rising healthcare costs. It has not been well-established that
defensive medicine exists, and, if it exists, whether reform of tort laws is effective in
reducing it. The importance of this study is in its contribution to determining whether tort
reform legislation is an effective approach to reducing defensive medicine and of
addressing rising cesarean delivery rates.
2
The purpose of this study was to investigate the effect of changes in tort law on
defensive medicine by examining changing patterns of cesarean section. This was done
by estimating the effects of changes in tort laws on cesarean section rates over the 1991
through 2004 period, taking advantage of recently collected information on state
legislation and court decisions over this period, nationwide birth certificate data, and
econometric techniques. Defensive medicine is a complex phenomenon, which has been
explored via research spanning several disciplines, including medicine, law, economics,
and policy. The present work draws on these disciplines while adding the perspective of
obstetrics, perinatal epidemiology, and maternal and child health.
3
CHAPTER 2
BACKGROUND
History of Cesarean Section
In generations past, death during childbirth and death of an infant were such
common experiences that a woman had little expectation of delivering a live, healthy
infant or of her own survival. Maternal deaths from complications of pregnancy
decreased by 99% during the last century, from 85 per 1,000 live births in 1900 to 7.5 in
1982 (no further decrease since that time). (3) In 1911, the infant mortality rate in the
United States was 135.0 per 1,000 live births (4) compared to 6.8 in 2007. (5) Improved
survival has resulted in changed expectations with respect to the birth experience and
fetal outcome.
For a thousand years, obstructed labor was managed by rotating the fetus so that
one foot, rather than the head, presented during delivery (referred to as a “footling
breech”). Delivery was accomplished by applying traction to the foot, and the head was
expelled via pressure on the maternal abdomen. (6) Before cesarean delivery came into
wide use for cephalopelvic disproportion (fetal head disproportionately large in relation
to the maternal pelvis), intervention to preserve the mother’s life often involved
craniotomy or cephalotripsy, cutting or collapsing of the fetal skull to allow passage
through the maternal pelvis. (7) Introduction of obstetric forceps in the mid-1800’s
reduced but did not eliminate the need for craniotomy. (8)
The first reported cases of cesarean performed on live women occurred in the 17th
century. (8) Prior to that time, cesarean delivery was a postmortem procedure intended to
save the infants of women who died late in pregnancy. (8) What is reportedly the first
4
cesarean delivery in the United States was performed in 1827 by Dr. Ephraim McDowell
in Newtown Ohio. (9) Cesarean in the United States began to evolve in the late 19th
century; however, according to one report of 100 cesarean deliveries performed in the
United States in 1878, 56% resulted in death of the mother. (8) These 100 cases were
drawn from among “lying-in” (maternity) hospitals, and other reports suggest that
mortality for cesarean in the community overall was higher.(8) Cesarean was a
procedure of last resort, used only in cases of cephalopelvic disproportion. (10) At that
time, CPD most often resulted from contracture of the maternal pelvis due to rickets, (11,
12) a condition which is rare in the United States today. Cesarean was recommended
only in cases where death of both mother and infant would be otherwise inevitable.
Whether it was preferable to perform a craniotomy on a live fetus, which would result in
death of the fetus, or attempt a cesarean, which carried high risk of death for the mother,
was a subject of controversy in the mid-1800’s. (8)
In the present day, the most common indications for which cesarean delivery is
performed are dystocia (failure to progress in labor), fetal distress, breech presentation,
and history of prior cesarean. (13) Dystocia can result from CPD, mal-position of the
fetus, or inadequate frequency and strength of maternal contractions. (11) These
indications are further described in a separate section below.
Several medical advances in the mid to late 19th century made cesarean delivery
more feasible and began to improve survival. Surgical anesthesia was first used in Boston
in 1847. First chloroform and then ether were introduced into obstetric practice.(8) The
germ theory of disease was advanced in the 1860’s, and Joseph Lister’s aseptic technique
utilizing carbolic acid spray was introduced into obstetrics in 1870. (6) Introduction of
5
antibiotics, sulfonamides in 1937 and penicillin in the 1940’s, (14) and safe blood
transfusions in the 1940’s (15) reduced maternal death from the two main causes,
infection and hemorrhage.
Two technological advances in the 1960’s, ultrasound and electronic fetal
monitoring (EFM) changed both the management of labor and delivery and the
perception of the fetus. Visualization of the fetus via ultrasound provides the clinician
with the opportunity to assess gestational age and to detect some types of fetal
abnormalities. Ultrasonography also provides the mother with an opportunity to view the
fetus, which was never before possible. EFM entails use of either an external or internal
device to detect heart rate patterns indicative of possible oxygen deprivation. Prompt
recognition of oxygen deprivation and delivery of the infant is thought to reduce the
likelihood of neurologic injury. Soon after its development, continuous EFM began to
replace intermittent auscultation by stethoscope to monitor the fetal heart rate. (16)
With advances in obstetric medicine and technology has come a perception that
reproductive outcomes can not only be predicted but controlled, leading to the
expectation of a perfect baby. (17) This belief can, in turn, lead to an assumption that an
imperfect outcome is the result of physician error and may lead to malpractice
lawsuits.(17) In sharp contrast with maternal expectations early in the last century,
advances in obstetric medicine have created the expectation of a problem-free delivery.
Increasing Cesarean Section Rates
Over the past four decades, cesarean births have increased as a percentage of all
births in the United States from 5.5% in 1970 to 32.9% in 2009 (preliminary data). (2)
6
Increases in the total rate reflect both increases in rates of primary cesarean and a sharp
drop in rates of vaginal delivery by women who have had a prior cesarean birth (VBAC).
Following dramatic increases in cesarean births in the 1970’s and ‘80’s, rates declined
between 1989 and 1996. (18) During this period, rates of primary cesarean decreased
and VBAC increased. (19) Since 1996, the rate of primary cesarean has increased, and
the rate of VBAC has decreased (with the rate of repeat cesarean consequently
increasing).(18) In 2006, the rate of repeat cesarean was approximately 92%; (19)
however, 53% of the overall increase in cesarean rates 1991-2002 was attributable to
increases in primary cesarean delivery. (20) The greatest reported variation in cesarean
delivery rates has been in nulliparas (women who have not previously given birth) with
singleton vertex pregnancies (one fetus presenting head first). (21)
Although no ideal rate of cesarean delivery has been established, there is wide
agreement that rates have become too high. The World Health Organization (WHO)
Consensus Statement, published in 1985, recommended an ideal rate of 10-15%. (22)
This rate has been widely criticized as lacking a firm evidence base, and according
WHO’s 2009 Monitoring Emergency Obstetric Care: A Handbook, “Both very low and
very high rates of caesarean section can be dangerous, but the optimum rate is unknown.”
(23) In 1990, the U.S. Public Health Service set a Healthy People 2000 goal of reducing
the rate of cesarean deliveries to 12% for primary cesarean deliveries and 65% for repeat
cesareans, for a 15% reduction in cesareans overall. This goal was not achieved, and
Healthy People 2010 Objective 16-9 specifies reduction of cesarean section rates to 15%
among women giving birth for the first time and to 63% of women who have undergone a
prior cesarean birth. These goals were developed by a U.S. Department of Health and
7
Human Services working group and are based on the lowest 25% of state rates for
primary cesarean delivery rates and the highest 75% of state rates for VBAC as
determined from 1996 NCHS birth certificate data. (24) At the time of 22010’s release,
cesarean section rates were decreasing but then resumed their pattern of increase.(25)
These objectives were recently again modified for Healthy People 2020, with a target of
23.9% for primary cesarean and 81.7% for repeat cesarean deliveries. (26)
Risks of Cesarean versus Vaginal Delivery
With increasing cesarean rates, concern has arisen that many of these surgeries
may not be truly indicated, exposing both mother and fetus to unnecessary risk.
Childbirth has always posed a danger to both mother and fetus, and there are risks
associated with both vaginal and cesarean birth.
As previously described, before cesarean came into use, serious complications
resulted in high rates of fetal and maternal mortality and morbidity. In the present day,
the most common adverse maternal outcome of vaginal delivery is urinary stress
incontinence. Vaginal delivery may cause injury to the nerves, muscles and connective
tissue of the pelvic floor, resulting in urinary or anal incontinence or prolapse of the
bowel, bladder or reproductive organs. Third degree laceration into the anal sphincter,
which is most common in deliveries involving forceps or episiotomy, may also result in
incontinence. (21) Some of these complications may result in long-term dysfunction.
Among the risks of vaginal delivery for the fetus are neurologic injury due to hypoxia
(oxygen deprivation) or brachial plexus injury (stretching of the network of nerves that
run from the cervical spine to the shoulder, arm, and hand) that may result from difficulty
in delivering the shoulders.
8
Although the purpose of cesarean delivery is to prevent adverse outcomes, it
carries the inherent risks of major abdominal surgery. Maternal mortality, although very
low in the United States (12.7 per 100,000 live births in 2007), (27) is reportedly 3-7
times greater for cesarean than vaginal delivery. (21) These deaths are most commonly
caused by deep vein thrombosis or pulmonary embolism. (21) Surgical complications of
cesarean may include hemorrhage, injury to the urinary tract, (13, 21) and, occasionally,
the gastrointestinal tract. (21) The most common postoperative complication of cesarean
delivery is infection, with endomyometritis (infection of uterine tissues occurring after a
cesarean section), estimated to occur in anywhere from 10-50% of cesarean
deliveries.(21) Women who have undergone cesarean experience increased risk of
complications in future pregnancies, including a three-fold increased risk of placenta
previa (placenta obstructing the cervical opening), (21) a rare but serious complication.
Placenta previa may lead to placenta accreta, where the placenta detaches from the
uterine wall and causes severe hemorrhage. (21) Longer term consequences of cesarean
may include pelvic pain, bowel obstruction, and threats to future reproductive capacity.
(28)
Although cesarean delivery has contributed to an impressive decrease in perinatal
mortality rates over the last century, the surgery does pose some risk to the fetus.
MacDorman et al, used 1999-2002 linked U.S. birth and death data to examine
differences in infant mortality among low risk (no prior cesarean, singleton birth, term
gestation, no medical risk factors, no placenta previa) delivering vaginally and via
cesarean. An ‘‘intention-to-treat’’ methodology, where both vaginal deliveries and
unplanned cesareans (labor and delivery complications recorded on the birth certificate)
9
were treated as though the intention was to delivery vaginally, was used to compare
planned cesarean deliveries (no labor and delivery complications recorded on the birth
certificate) to planned vaginal deliveries, adjusting for socio-demographic and medical
risk factors. They reported an adjusted odds ratio for neonatal mortality of 1.69 (95% CI
1.35–2.11) for cesareans with no labor complications or procedures, compared with
planned vaginal deliveries. (29) Potential harm to the fetus may include surgical cuts,
respiratory distress, and development of childhood asthma. (28) While in utero, the fetal
lungs are filled with fluid. It is thought that the process of labor may assist in clearing this
fluid in preparation for birth. (30) Cesarean delivery interrupts this process. Also, some
cases of respiratory distress in neonates delivered via cesarean may be due to iatrogenic
prematurity, which occurs when the gestational age of the fetus was inaccurately
estimated prior to delivery, resulting in a premature birth. (30)
Between 1996 and 2004, the percentage of cesareans that were repeat, rather than
primary, surgeries increased from 71.7 to 90.8%. (31) This increase has been attributed to
the decrease in vaginal birth after cesarean (VBAC) in response to concern over reported
risks. Risks associated with repeat cesarean are similar to those for primary cesarean;
however, there are some additional risks. Maternal morbidity (placenta accreta, bowel or
bladder injury), postoperative ventilation, intensive care unit admission, hysterectomy,
blood transfusion requiring four or more units, duration of surgery, and length of hospital
stay, increase progressively with the number of cesarean deliveries. (32) Menacker et al.
report an adjusted odds ratio for neonatal mortality for repeat cesarean delivery compared
with VBAC of 1.36 in low risk (singleton, term, vertex presentation) pregnancies 1998-
10
2002, with rates of repeat cesarean delivery for low risk pregnancies comparable to rates
of repeat cesarean overall. (33)
The decreasing rate of vaginal birth after cesarean (VBAC) was influenced by the
risk of uterine rupture. This risk may have been overstated in some past reports; however,
uterine rupture remains a serious (although rare) complication. Guise et al., (34) in a
recent systematic review, found that a number of studies used a broad definition of
“rupture” that included separation of the uterine scar without symptomatic rupture, over-
estimating the incidence of uterine rupture. Excluding those studies, Guise et al. (34)
reported the rate of uterine rupture among women undergoing a trial of labor as 0.47%
and for elective repeat cesarean as 0.30%, with the difference reaching statistical
significance. They also reported significantly greater perinatal mortality (0.13%) for trial
of labor compared to elective repeated cesarean (0.05%). Rates of maternal hysterectomy,
hemorrhage, and transfusion did not differ significantly between the two procedures.(34)
Several factors are believed to have influenced trends in cesarean section. The
increase in rates between the mid-1960s and the late 1980s has been attributed to
changing maternal characteristics (older maternal age, reduced parity), increasing
incidence of risk factors (maternal obesity and diabetes, macrosomia), (35) changes in
obstetric practice (increased use of epidural anesthesia, fetal monitoring, cesarean
delivery for breech presentation, and reduced use of forceps), (35) and social factors
(malpractice litigation and socioeconomic factors). (35) However, recent dramatic
increases, particularly since the mid-1990s, are less understood. There have been widely
conflicting reports with respect to the extent of maternal preference for cesarean and its
contribution to rising cesarean rates, with much of the evidence anecdotal. Maternal
11
request cesarean is difficult to quantify, (36) and many studies purporting to examine
“maternal request” cesarean include no measure of intent but rather examine cesarean
with no documented medical indication. (18) Cesarean section rates vary substantially by
geographic location within the United States. Some of this variation is explained by
differing patient characteristics, provider density, and other aspects of local health care
delivery; however, otherwise unexplained variation has been attributed to local variation
in physician practice style. (37)
Clinical Indications for Cesarean Delivery
A “high risk” pregnancy is a pregnancy at greater than normal risk of
complications, either of pregnancy or labor and delivery. A pregnancy may be considered
high risk if one or more of a number of medical conditions are present, including renal,
cardiac or endocrine disease, fetal anomalies, history of pre-term delivery, incompetent
cervix, RH incompatibility between mother and fetus, mother is a carrier of a genetic
disorder, multiple gestation, placenta previa after 28 weeks, prior fetal death,
hypertension, diabetes, asthma, or third-trimester bleeding. The majority of these
conditions are included among the check-box items on the birth certificate. (38) In
pregnancies at high risk for fetal loss, tests of fetal well-being may be performed
beginning at 28 to 32 weeks gestation. Testing is often performed in the presence of
decreased fetal movement, fetal growth restriction, or a post-term pregnancy, as well as
in the presence of hypertension, diabetes, multiple gestation with discordant fetal growth,
oligohydramnios (diminished amniotic fluid volume) or polyhydramnios (excess
amniotic fluid volume), post-term pregnancy, or prior loss or stillbirth. (38) This testing
12
may entail either cardiac stress or non-stress testing employing an electronic fetal monitor
and ultrasonography. (38)
The majority of primary cesarean deliveries are performed because of dystocia,
non-reassuring fetal heart rate, or breech or other malpresentation. (12) (ACOG has
recommended that the term “fetal distress” be replaced by “non-reassuring fetal heart
rate,” which is more specific.) (39) Another 3% of cesarean deliveries were performed as
a result of unsuccessful trial of forceps or vacuum extraction. All other indications
combined account for just 15% of cesareans. (12) Because many repeat cesareans are
performed because a cesarean for dystocia was performed in a previous pregnancy, 60%
of cesareans are directly or indirectly attributable to dystocia. (40) Table 1 below
presents complications of pregnancy and of labor and delivery according to the
percentage occurring in all singleton births, in singleton cesarean births, and the
percentage of cesarean births in which each complication occurs, 1991-2002. For
example, although cephalopelvic disproportion is reported in just 2% of all singleton
births and in 10% of singleton cesarean births, cesarean delivery is reported for 97% of
singleton births for which cephalopelvic disproportion is recorded as a complication.
Note that labor and delivery complications are likely underreported in the birth certificate
data. (41) This underreporting is further discussed in Chapters 2 and 3. Additionally,
more than one complication may be reported per birth, and co-occurring complications
may be associated with each other.
13
Table 1. Percent of Reported* Pregnancy and Labor and Delivery Complications, U.S. Standard Certificate of Live Birth (1989 Revision), 1991-2002**
Percent of Live
Singleton Births with
Complication Reported
Percent of Singleton
Cesarean Births with
Complication Reported
Percent of Singleton
Births with Complication Reported that
were Delivered by Cesarean
Pregnancy complications Pregnancy-associated hypertension 3.27 5.59 36.03 Diabetes 2.64 4.49 35.92 Hydramnios/Oligohydramnios 1.11 1.95 37.00 Anemia 2.06 2.14 21.89 Herpes 0.79 1.37 36.41 Chronic hypertension 0.69 1.31 40.17 Previous infant > 4000 g 1.04 1.28 26.09 Previous preterm infant 1.14 1.23 22.66 Lung 0.82 0.96 24.71 Eclampsia 0.31 0.70 47.89 RH sensitization 0.63 0.65 21.82 Cardiac 0.47 0.55 24.83 Incompetent cervix 0.23 0.32 29.51 Renal disease 0.26 0.31 25.15 Hemoglobinopathy 0.07 0.08 25.07 Labor and Delivery Complications Breech 3.18 12.90 85.51 Fetal distress 3.67 9.97 57.40 Cephalopelvic disproportion 2.27 10.33 97.01 Dysfunctional labor 2.82 8.75 65.95 Meconium 5.65 5.65 21.09 Premature rupture of membranes 2.68 3.14 24.67 Febrile 5.65 5.65 21.09 Abruptio placenta 0.54 1.50 58.18 Prolonged labor 0.86 1.47 36.34 Placenta previa 0.32 1.25 81.47 Excessive bleeding 0.55 0.75 28.69 Seizures 0.04 0.08 48.71 Cord prolapse 0.20 0.61 64.94 * As sensitivity for some variables is reportedly less than 40%, figures presented for some complications may be extreme underestimates. ** As reported on the Unrevised (1989) U.S. Standard Certificate of Live Birth. In 2003, 2 states (Pennsylvania, Washington) began using the 2003 revised birth certificate. In 2004, the 2003 births certificate was in use by an additional 7 states (Idaho, Kentucky, and New York, excluding New York City, South Carolina, Tennessee, Florida, and New Hampshire), accounting for 20% of all live births. The majority of complications are not comparable across birth certificate revisions. We have therefore presented these data for the years 1991-2002 only.
14
Complications of pregnancy that contribute to the risk of undergoing a cesarean
delivery include hypertensive disorders (chronic hypertension, pregnancy-associated
hypertension, preeclampsia, and eclampsia), hemorrhage (bleeding from the site of
placental attachment or from the genital tract), pre- or post-term pregnancy, fetal growth
retardation, twins or higher order multiples, and fetal abnormalities. Preeclampsia is the
development of hypertension plus proteinuria or generalized edema during pregnancy and
may progress to eclampsia, which is characterized by convulsions. Hypertension
increases the risk of abruptio placenta and of fetal growth retardation and intrauterine
death.
Estimates of the proportion of deliveries attributable to these indications vary. The
recent literature on cesarean emphasizes the practical and ethical implications of VBAC
and maternal choice cesarean, and there has been little published in the last decade on the
indications for cesarean section. The majority of published papers describing population-
based estimates of cesarean rates by indication and risk factors are ten or more years old
and are based on data now 15 or more years old. It is therefore difficult to assess trends
in indications and risk factors for cesarean over time. A limited analysis based on birth
certificate data is presented in Table 1.
“Dystocia” is used to describe abnormal labor, specifically, prolonged or arrested
cervical dilation or arrested fetal descent. The diagnosis of dystocia increased over time
and, according to some reports, accounts for approximately 60% of primary cesarean
deliveries. (12) Increasing use of epidural anesthesia, (12) the increasing prevalence of
maternal obesity, (42) and inadequate use of oxytocin augmentation in women failing to
progress in labor (12) may have contributed to the increase in dystocia; however, there is
15
a widespread belief that dystocia is over diagnosed. (12) This over-diagnosis has been
attributed in part to misdiagnosis and variability in the criteria for diagnosis but also to
fear of litigation. (12) Gifford et al. (2000) reported that despite ACOG’s
recommendation that dystocia not be diagnosed until cervical dilation reaches 3-4 cm,
25% of cesarean deliveries for dystocia were performed at 3 cm or less. According to
ACOG, “there is much uncertainty about the definition of the latent phase of labor.”
There is, however, agreement that the active phase begins when cervical dilation is
between 3 and 4 cm, (40) and that it is not possible to diagnose dystocia until labor
progresses from the latent to the active phase. (42)
The second most common reason reported for performing a cesarean is non-
reassuring fetal heart rate (fetal distress), (13, 43) which is diagnosed primarily via
electronic fetal monitoring (EFM). EFM entails use of either an external or internal
device to detect heart rate patterns indicative of possible oxygen deprivation. Prompt
recognition of oxygen deprivation and delivery of the infant is thought to reduce the
likelihood of neurologic injury of the fetus, particularly cerebral palsy. EFM use
increased from 45% of pregnant women in labor in 1980 to 85% in 2002. (13, 43) A
diagnosis of fetal distress based on EFM is subject to many false positives, and there is
substantial intraobserver variability in obstetricians’ interpretation of fetal heart rate
patterns.(44), (45) Despite the increase in EFM and in cesareans, rates of cerebral palsy
have remained constant over time at approximately 2.0 per 1,000 live births. (44)
Williams’ Obstetrics refers to diagnosis of fetal distress based on fetal heart rate patterns
as “imprecise and controversial.” (46) Additionally, according Bassett et al., significant
16
reversible hypoxia, which EFM is intended to identify, is rare, occurring in just 1-2% of
births. (43)
Conventional wisdom for many years dictated that following a cesarean, all
subsequent pregnancies be delivered via cesarean. Evidence began to accumulate that a
trial of labor might be appropriate for some women with a history of cesarean. It became
increasingly common to allow women who had previously undergone a cesarean to
proceed with a “trial of labor.” These attempts at vaginal delivery were mandated by
some insurance carriers, and physicians were reportedly pressured to allow trials of labor
for unsuitable patients. Between 1985 and 1996, VBAC rates increased from 5% to 28 %.
(47, 48) VBAC carries a risk of rupture of the uterine scar. Although this risk is
extremely small the consequences can be catastrophic, and may result in the mother’s
undergoing a hysterectomy or in death or neurologic injury to the infant. (48) As VBAC
rates increased, an increase in cases of uterine rupture occurred, and in some of these
cases, malpractice lawsuits were filed. Following publication of a number of articles (33)
and an influential 2001 editorial recommending against VBAC, (49) rates again began to
drop. In 2002, the VBAC rate was 8.5%. (47), and for 2006, the rate was 7.6% among the
31 states using the 1989 U.S. Standard Birth Certificate and 8.5% among the 19 states
using the 2003 revised certificate. (19) (VBAC is not comparable across birth certificate
revisions.) (19) ACOG’s 2004 guidelines recommended that VBAC be permitted only
under circumstances where emergency cesarean was available within 30 minutes of a
decision to perform surgery. These guidelines were narrowly construed, and many
hospitals and insurance companies ceased allowing VBAC. (50) Recent research has
17
challenged the preference for repeat cesarean over VBAC for certain low risk women. In
August of 2010, ACOG issued a revised guideline providing clarification. (47)
A number of the risk factors and complications that would influence the decision
to perform a cesarean section have changed in either incidence or prevalence over time.
Increasing numbers of women have delayed motherhood until after age 35, which carries
increased risk of delivering a preterm or low birthweight infant. (51) Birthweight has
increased over time, resulting in increases in the incidence of macrosomia (birthweight >
4,000 grams). (51) Prevalence of type II diabetes, (52) gestational diabetes (53, 54) and
hypertension (52) have increased in recent decades . The prevalence of obesity in the
United States has increased dramatically over the past 30 years, (55) and currently nearly
50% of women of childbearing age in the United States are overweight or obese. (56) A
number of studies have suggested that being overweight or obese increases a woman’s
risk of prolonged labor (57, 58) and dystocia, even in the absence of other complications.
(42) Other obstetric complications more common among pregnant women who are
overweight or obese are hypertensive disorders and diabetes.(19) Rates of pre-term birth
have risen 20% (14% among singleton births) and low birthweight 10% since 1990. (59)
Twins and higher order multiples, the occurrence of which has increased in recent
decades, are more likely to be delivered by cesarean section. (60) Nevertheless, studies
have concluded that changes in the medical risk profile over time are not the major
contributors to the increase in rates. (61)
There have been dramatic changes over time in the percentage of infants delivered
via cesarean section, with substantial geographic variation. (37) Practice variation
specific to cesarean had not been well-explained; however, there been considerable
18
research on physician practice variation generally. According to Eisenberg, (62) practice
variation results from a complex set of factors, which can be categorized as those
benefitting the physician, those benefitting patients, and those benefitting society overall.
(One factor that drives variation is underlying uncertainty about best practices. To non-
clinicians, many medical decisions may appear to be clear-cut and based on firmly
established diagnostic and treatment criteria; however, health services research
demonstrates that there is a great deal of uncertainty involved in the practice of medicine.
This uncertainty occurs because scientific evidence may be ambiguous, incomplete, or
conflicting. (63, 64) Procedures for which there is consensus among physicians and broad
scientific support in the literature are associated with little variation in practice; however,
for many procedures, norms are not well-defined. (63) Practice variations also result
from differences in observation and interpretation of tests and of clinical signs and
symptoms among individual physicians. (64) Provision of medical services is based on
science but is also influenced by subjective factors, including physician attitudes,
opinions, and personal experience in the practice of medicine. Wennberg, a preeminent
researcher in the area of physician practice variation, refers to these influences as the
“practice style factor.” (63) The daunting task of synthesizing complex, conflicting, and
ambiguous information and determining how best to apply that information to the clinical
circumstances of an individual patient may lead to oversimplification and to broad
application of rules of thumb. (64) In the face of uncertainty about approach to
management of a particular condition, a physician often follows a course consistent with
that of other physicians in the community in which he or she practices, which becomes
the standard for the community. (64) This may in some cases cause defensive medicine to
19
effectively become the standard of care. (65) Differences in standards across
communities exist, because there is insufficient evidence to clearly support one course of
action and different conclusions with respect to best practices are drawn. (64)
In the case of obstetrics, many guidelines, best practices based on a thorough
review of the available scientific evidence, are established by ACOG. How those
guidelines are interpreted and implemented may differ among institutions and among
geographic areas, resulting in practice variations. The significant disparity in
interpretation of the 1998 and 2004 ACOG VBAC guidelines with respect to immediate
availability of emergency care is an example.
Whereas empirical studies treat the decision to perform a cesarean as one based
on a checklist of evidence-based indicators, many clinicians argue that the emphasis on
rigid criteria ignores the role of individual clinical judgment with regard to the most
beneficial course for an individual patient. (66) The literature on medical uncertainty and
practice variation, the role of individual clinical judgment, and the influence of changing
thresholds for some labor and delivery complications suggest that the gray area between
“necessary” and “unnecessary” cesarean may be larger than widely perceived. Therefore
empirical studies categorizing cesareans as “necessary” or “unnecessary” are inherently flawed.
Those using birth certificate data, for which many of the indications are poorly reported, are even
more so.
Liability Pressure and Defensive Medicine
Medical negligence is an act or omission by a health care provider that deviates
from the standard of care in the relevant medical community as defined by state laws. If
the negligence results in injury to the patient, there is a breach of professional duty
20
actionable under tort law. Physicians are expected to conform to a standard defined by
the “degree of skill and care that a physician or surgeon of the same medical specialty
would use under similar circumstances.” (67) The standard of care “in the community” is
generally construed to refer to local practice patterns; however, legal rulings have left
some uncertainty as to the geographic scope of a community. (68)
Most medical malpractice claims sound in tort (have their basis in tort law). A tort
is defined as a private or civil wrong resulting from breach of a legal duty. (69) Such a
wrong may be redressed via a lawsuit leading to an award of damages. The injured party
may be compensated for economic (e.g., past and future medical expenses and past and
future lost wages) and non-economic (e.g., pain and suffering) damages). (70) Torts are
classified as intentional, negligent, or strict liability (i.e., liability for defective products)
torts. Negligence is typically defined as the “failure to behave with the level of care that
someone of ordinary prudence would have exercised under the same circumstances,” and
can consist either of acts or omissions. (70) To establish negligence, the five elements of
the “negligence rule” must be demonstrated. There must be: 1) a duty to exercise
reasonable care; 2) an act or omission that breaches that duty; 3) the act or omission must
be the cause of the harm (actual cause); 4) the act or omission must be fairly closely
related to the harm, rather than a remote consequence, (proximate cause); and, 5) the
harm must have monetary value (damages). (70)
Most medical malpractice tort claims sound in negligence, but traditionally
medical malpractice claims have been treated differently than other negligence claims.
Instead of using the reasonable prudent person standard, courts have traditionally used a
customary standard whereby the conduct of the defendant physician is compared to
21
accepted practices in the profession. The jury in a medical malpractice case is charged
with determining what is customary practice and whether the physician was in
compliance with that practice, rather than whether the physician acted in a reasonable
manner. (71) Physicians are held to this alternative standard because of their unique
training and expertise, (72) which has over the past century been rewarded with deference
and special privilege. (71) The custom-based standard arose, because it was believed that
a lay jury would have insufficient knowledge to assess reasonableness of medical care
and because it was believed inappropriate to compare the actions of physicians, who are
ethically bound to hold the interests of their patients first, with for-profit endeavors or the
actions of persons otherwise acting in their own interest. (72)
From the custom standard have arisen a number of doctrines bearing on
malpractice actions. In a medical malpractice case, each side, plaintiff and defendant,
endeavor to prove their cases via testimony of expert witnesses who educate the jury
about customary medical practice and address whether or not the defendant’s practices
were consistent with the applicable “standard of care.” The standard of care is not
limited to one medical custom but is rather subject to a “two schools of thought” or
“respectable minority” rule, which allows physicians to choose between conflicting but
respectable approaches to treatment when medical opinion is divided. (71) The standard
of care has been traditionally defined according to medical custom at the local level, and
expert witness testimony was subject to a “locality rule,” requiring the expert to be
familiar with customary practices specific to the community in which the defendant
physician practiced. Beginning in the 1970’s there was gradual dismantling of the
locality rule. The rule had been established in part to protect rural physicians against
22
being held to the same standard as their urban counterparts who had greater access to
state of the art knowledge and better conditions in which to practice; (72) however,
plaintiffs found it difficult to retain expert witnesses willing to testify against their local
peers. (72) There has been a gradual shift toward reliance on nationwide medical custom,
particularly for specialists
More recently, it has been argued that many courts have shifted from the
customary standard to a reasonable prudent physician standard. (71, 72) This shift in
judicial interpretation of malpractice law began in the 1970’s. (71) Multiple court
decisions, beginning with a 1965 Illinois Supreme Court case (Darling v. Charleston
Community Memorial Hospital), have taken the position that adherence to custom should
not be considered conclusive evidence in support of appropriate care, because the custom
itself could be unreasonable or negligent. (71) Courts rejecting the custom standard have
opined that an industry should not be permitted to establish its own standard of care, (71)
reflecting a gradual decline in deference toward physicians by both the lay public and the
judiciary. (71) Another criticism of the custom-based standard is that physicians do not
know how other physicians practice medicine. (72) As such, the testimony of expert
witnesses is typically about the care they would have provided under similar
circumstances, (72) what they believe to be reasonable, rather than what is truly
customary. Over time some states have rejected the custom-based or begun to apply it
more loosely. Among the implications of this shift is that expert testimony demonstrating
the defendant physician’s compliance with accepted practice is no longer a complete
defense, and there is increasing uncertainty regarding the standard of care. This
uncertainty may lead to an increase in defensive medicine. (71)
23
The principal goals of the tort system are to deter negligent conduct and
compensate the injured parties. In addition, corrective justice has been identified as a
third goal of tort law. The purpose of tort liability in the context of medical malpractice is
to provide incentives for the optimal level of precaution and to limit inappropriate or
negligent care, (73) thus exerting “liability pressure.”
Although physicians’ legal expenses (settlement, judgment, attorneys’ fees, court
costs) are for the most part covered by insurance, non-monetary costs of a malpractice
lawsuit may be substantial, including time spent (e.g., responding to interrogatories,
undergoing depositions, attending court appearances) adverse publicity, a blemished
reputation, and significant personal distress. (74, 75) Ideally, the tort system should exert
some optimum level of liability pressure, which would maximize social benefit. If
liability pressure is too low, physicians may provide too low a level of care. If the level of
malpractice pressure is too high, doctors may take excessive precautions. The marginal
cost to society of these precautions may exceed the marginal benefits, which is referred to
as “defensive medicine.”
Defensive medicine, as defined by the U.S. Office of Management and Budget,
“occurs when doctors order tests, procedures or visits, or avoid high risk patients or
procedures primarily (but not necessarily solely) to reduce their exposure to medical
malpractice liability.” (76) These tests, procedures or visits may be appropriate and
reasonable, but if they are intended primarily to benefit the physician by protecting
against liability they are considered defensive. (77) Defensive medicine may benefit both
the physician and the patient, and may result in enhanced health care for the patient;
however, in economic terms, the marginal cost of the procedure exceeds the marginal
24
benefits. Klingman et al., in the belief that labeling of care as unnecessary or unjustified
indicates clearer delineation between appropriate or inappropriate care than actually
exists, proposed that defensive medicine be defined as “actions taken to minimize the
chance of being wrong when the medical and legal consequences of being wrong are
severe.” (78) They further refine their definition by dividing defensive medicine into
four categories, procedures that raise costs while reducing quality, those that raise costs
while raising quality, those that reduce costs while reducing quality, and those that raise
costs while reducing quality. (78)
Defensive medicine occurs in two forms, “positive defensive medicine,” the use
of additional tests or procedures, and “negative defensive medicine,” avoidance of tests,
procedures, or groups of patients that may be associated with a high risk of adverse
outcome in order to minimize liability risk. (76, 79) In a survey of physicians practicing
in several high-liability specialties (emergency medicine, general surgery, orthopedic
surgery, neurosurgery, obstetrics/gynecology, and radiology), conducted by Studdert et
al., 93% reported performing additional tests, diagnostic procedures and referrals for
consultation to minimize the possibility of litigation. (80) In a survey conducted by
Carrier et al. of a nationwide sample of physicians, 67.7% of respondents reported
concern over malpractice risk and 62% reported engaging in defensive medicine. Among
obstetrician/gynecologists, these percentages were 81.0% and 68.5%. (81) Physicians
also report negative defensive or avoidance behavior. In the study by Studdert et al., (80)
of high risk specialists, 46% of obstetrician/gynecologists reported that they avoid caring
for high risk patients and 38% reported that they avoid certain procedures or
interventions.
25
Mailed surveys are subject to both selection and reporting bias, as there is a
tendency for those who respond to be those motivated by strong opinions, and there is a
tendency to respond to questions in socially desirable ways. (82) Consequently, physician
surveys may overstate the extent of defensive medicine, with those favoring tort reform
over-represented among respondents and, consciously or unconsciously, over-reporting
their practice of defensive medicine. (83) Studies that query physicians on how they
would address each of a series of specific clinical scenarios have reported markedly
lower percentages of physicians practicing defensive medicine. Klingman et al. employed
a mailed survey describing nine clinical scenarios to assess defensive medicine practices
in a random sample of U.S. cardiologists, surgeons, and obstetrician/gynecologists.
Among 54 clinical actions that the survey proposed in response to the scenarios, 8%
(median) were selected primarily to minimize malpractice risk. (78) Results of clinical
scenario studies may be more reliable than direct surveys but are less generalizeable. (78)
If defensive medicine is practiced in response to liability pressure, we would
expect to see this manifested in obstetric practice, as obstetricians are sued more
frequently and are charged higher premiums for malpractice insurance than physicians in
other medical specialties. (84) Among respondents to the 2009 American College of
Obstetricians and Gynecologists (ACOG) Survey on Professional Liability, 90.5%
reported at least one professional liability claim during their careers. (85) Accordingly,
one would expect that obstetricians are more attuned to the potential impact of increases
in premiums and the potential for litigation than practitioners of other specialties and to
react defensively. Also among 2009 ACOG survey respondents, 30.2% reported
decreasing the number of high-risk obstetric patients in their care, 29.1% reported
26
increasing the number cesarean deliveries they perform, and 25.9% reported that they
have stopped performing VBAC. (85)
What is often described as the “malpractice crisis,” characterized by dramatic
increases in malpractice insurance premiums and/or the exit of firms from the malpractice
insurance market, has come in three waves, beginning in the mid-1970’s. Each wave has
spurred enactment of changes in tort laws, referred to hereinafter as “tort reforms,” in
many states. The term “tort reform” is sometimes associated with advocacy but used here
to conform to the language of other academic papers on this topic. The primary intent of
these tort reforms has been to constrain the growth of malpractice premiums by reducing
the number of lawsuits and the size of judgments. It has also been argued that reforms
will increase access to care by increasing physician supply and willingness of physicians
to perform riskier procedures and take on higher risk patients, reducing the practice of
negative defensive medicine. Moreover it has typically been argued that tort reform will
reduce costs by reducing positive defensive medicine. The debate on health care reform
often includes discussion of tort reform, based on a belief by some that costs of the
medical liability system generally, and specifically defensive medicine, are major
contributors to rising health care costs. (86) The Congressional Budget Office (CBO)
has estimated that malpractice-related costs (insurance premiums, settlement awards,
administrative costs not covered by insurance) comprise approximately 2% of total health
care expenditures in the United States. (87) They propose that a package of tort reforms
would reduce health care spending by 0.5%, comprised of a 0.2% reduction in direct
costs, such as malpractice insurance premiums, and 0.3% in indirect costs, such as
reduced defensive use of medical tests and procedures. (87) Some studies have reported
27
findings that conflict with those of the CBO, such as Avraham et al., (88) who reported
that tort reform reduced health care costs, and Morrisey et al., (89) who reported that
savings from reducing medical liability insurance premiums were not passed on to
consumers or employers in lower health insurance costs.
Although tort reform in many states has been enacted in response to perceived
crises in medical malpractice, medical malpractice actions comprise just 15% of tort
litigation, with litigation related to automobile crashes accounting for 53% (based on
numbers of tort trials in 75 largest U.S. counties in 2001). (90) Tort reforms enacted in
some states, particularly non-economic damages caps, are limited to medical malpractice
actions. (90)
The standard menu of tort reforms adopted by many state legislatures as a
response to the recurring medical liability insurance crises are intended to reduce
excessive compensation for plaintiffs and deter the filing of frivolous claims. (73)
Although the specific measures have differed across states, many states have modeled
their reforms after California’s Medical Injury Compensation Reform Act (MICRA)
enacted in 1975, adopting some its components but not others. Among the provisions of
MICRA are a cap on non-economic damages ($250,000), modification or abrogation of
the collateral source rule to permit the defendant to introduce evidence of collateral
source payments, limits on plaintiff attorney’s fees, periodic payment of future damages
awards of $50,000 or greater, strict time limitations for presentation of a claim (statute of
limitations), and a provision for binding arbitration (California Code of Civil Procedure).
In states that have not enacted liability-reducing tort reforms, there are few
disincentives to file suit and the amount of recovery is theoretically unlimited. If fear of
28
lawsuits and their economic, social and psychological consequences are an incentive to
practice defensive medicine, one would expect to see a decrease in certain tests and other
medical procedures following implementation of tort reform in those states that have
implemented it, and no decrease in states that have not implemented tort reform.
By studying the effect of these reforms, defensive medicine can be studied more directly
than by using premiums or claims history as measures of liability pressure.
Literature on Tort Reform and Defensive Medicine
Tort reforms reduce the number and size of damage awards, (90-92) with some
reforms directly affecting the amount of recovery and others having an indirect effect by
reducing the number of lawsuits. Research has examined the effect of tort reforms on a
number of outcomes related to medical malpractice, among them claims frequency and
cost, medical liability system overhead costs, providers’ liability costs, defensive
medicine (including health care utilization and spending and medical outcomes),supply
of health care services (including physician supply and patient health insurance
coverage), and quality of care. (93) This has resulted in a wide body of literature, which
will be only selectively reviewed here. The figure below, adapted from Morrisey et al.
(89), is a depiction of the effect of tort reforms and the relationship among several the
branches of literature on tort reforms and medical malpractice presented.
The discussion to follow will focus on tort reform and defensive medicine but
briefly describe research that has been conducted on the effect of tort reforms on
malpractice insurance premiums and on physician supply. It will also describe research
on physician history of insurance claims and of lawsuits on defensive medicine.
29
Figure 1. Relationship Among Several Branches of Tort Reform Literature
Early empirical studies of defensive medicine measured liability pressure via
malpractice premiums, insurance claims history, history of malpractice lawsuits, and
perceived risk of lawsuits obtained via physician survey. Several studies conducted after
the first malpractice crisis examined the effect of liability pressure on cesarean rates.
Rock (94) examined the effect of malpractice insurance premiums for obstetricians on
cesarean rates in New York and Illinois and reported a statistically significant correlation
between differences in cesarean rates and differences in liability premiums for insurance
territories in each state. Localio et al. (95) used hospital discharge data linked with
physician and hospital malpractice claims records using a stratified random sample of
hospitals in New York State, controlling for clinical risk of cesarean, patient
socioeconomic status and physicians and hospital characteristics. They reported positive
associations between malpractice claims risk and cesarean rates and between physicians’
perceived risk of suit and cesarean rates. No significant association between odds of
cesarean and claims history of physicians was found. Baldwin et al. (96) examined the
effect of malpractice claims for a random sample of obstetricians and family physicians
Tort Reforms
Number & Size of Awards
Defensive Medicine
Malpractice Insurance Premiums
Physician Supply
30
during a one-year period on several obstetric care measures (ultrasound , referral and
consultation, prenatal care, cesarean) for low risk patients and found no increase in
resource use by physicians with a history of malpractice claims or in counties with high
rates of malpractice litigation. Tussing et al. (97) investigated the effect of malpractice
lawsuits on use of electronic fetal monitoring, diagnosis of fetal distress, and cesarean
section in New York State and found malpractice exposure to be associated with each of
the outcomes.
A limitation common to these studies four studies examining cesarean delivery
rates is use of data from one or two states and just a few years to estimate the effects of
malpractice liability. This limits their generalizability to other geographic areas and time
periods, as cesarean section rates and a broad range of economic, political and
demographic factors have varied considerably by state and over time. (98)
Several later studies (Table 2) also examined liability pressure via either
malpractice premiums or claims, each reporting some evidence of defensive medicine.
Grant and McGinnis (99), using 1992-95 Florida hospital discharge and insurance claims
data, concluded that exposure to medical malpractice liability led to a 1% increase in the
risk-adjusted cesarean section rate. Baicker and Chandra (2005) (98) examined the
effects of changes in malpractice premiums, the state-level effects of claims payments on
premiums, and the effect of malpractice liability on the physician workforce and on
several medical procedures, including cesarean, and reported a decrease in cesarean
section in response to increased premiums. Kim (2007) (100) used 1992-98 NCHS
natality data (1992-98) and malpractice claim information from National Practitioners
Data Bank to investigate the effect of malpractice risk on use of several obstetric and
31
gynecologic procedures, including cesarean section. Kim found that doctors’ procedure
choices were generally insensitive to malpractice risk, although there was a small but
statistically significant association between increased malpractice risk and use of
amniocentesis. Dranove and Gron (101) explored negative defensive medicine by using
Florida hospital inpatient data to examine physician activity and patient access with
respect to craniotomy and for cesarean section with complications. They compared
periods before and after a dramatic increase in insurance premiums (1997-2000, 2000-
2003) and found decreases in the number of physicians performing craniotomies, in the
number of physicians performing high risk deliveries, and in the number of craniotomies
performed by high volume neurosurgeons. For both neurosurgery and obstetrics, they
found low-volume providers decreased or ceased performing craniotomies or high risk
deliveries. The authors attribute these findings to increases in malpractice premiums
Baicker et al. (2006) used NCHS linked birth and death data pooled across 1995-98 to
calculate a probability, based on the patient’s pre-birth characteristics and removing the
effect of area characteristics unchanging over time, that a typical obstetrician would
perform a cesarean delivery. For each county, a risk-adjusted probability of receiving a
cesarean delivery was calculated. They reported that that average birth via cesarean has a
systematically lower predicted probability in areas that do more cesarean sections. The
authors conclude that counties with higher rates of cesarean may perform a greater
number of unnecessary cesareans; however, it is possible that important predictors were
omitted or inaccurately measured.
The incentive to practice defensive medicine is fear of liability. Tort reform
reduces the likelihood of suit (90) and the amount of any potential award, (90, 92) which
32
should reduce the fear of liability and the practice of defensive medicine. Response to tort
reform is a more direct measure of defensive medicine than insurance premiums
The first study to use changes in tort law to examine defensive medicine is
described in the seminal 1996 paper by Kessler and McClellan. (102) The authors
evaluated the effects of two sets of tort reforms, direct reforms (caps on non-economic
damages, caps on or elimination of punitive damages awards, elimination of mandatory
prejudgment interest, collateral source offset) and indirect reforms (limits on contingency
fees, periodic payment of awards, modification of the joint and several liability rule,
patient compensation fund, statutes of limitations or repose) on hospital expenditures
among Medicare beneficiaries following hospitalization for acute myocardial infarction
(AMI) or ischemic heart disease, 1-year survival, and experiencing a subsequent AMI or
heart failure. Direct and indirect tort reforms were used, because previous studies have
shown different effects of these two groups of reforms on claims payments and
frequency. Kessler and McClellan found that direct tort reforms reduced medical
expenditures 5-9% but found no effect on survival or on subsequent hospitalizations for
AMI or heart failure. Kessler and McClellan’s work has many strengths and has been
cited extensively by other authors, but it has also been argued that their findings are not
generalizable to settings outside the hospital, to medical conditions other than heart
disease, or to younger patients. (103, 104)
Since publication of the Kessler paper, several additional studies, summarized in
Table 2, have investigated the effect of tort reform on health outcomes. (104) Dubay et al.
(1999), (105) in the first national study to examine the effect of malpractice claims risk
on cesarean section and birth outcomes, investigated the effect of malpractice premiums
33
on cesarean rates, using six tort reforms as instrumental variables. They reported that an
increase in premiums resulted in an increase in cesareans but not an improvement in birth
outcomes (Apgar scores). For unmarried women of lower educational attainment,
increased premiums resulted in lower Apgar scores. They then estimated the effect of
tort reforms on malpractice premiums and estimated that a damage cap results in a 58%
reduction in annual premiums, which would result in a 0.48% decrease in cesarean
sections. Currie et al. (106) examined effects of four direct reforms, any punitive
damages cap, and non-economic damages cap, joint and several liability reform, and
common law collateral source rule in 25 states with changes in tort law (1989-2001) and
found that joint and several liability reform significantly reduced probability of cesarean
and damage caps increased it. Sloan et al. (104) building on the work of Kessler and
McClellan), (102) assessed the effects of tort reforms on Medicare payments for hospital
admission for AMI, stroke, breast cancer, diabetes and the probability of survival
following the index event. Rather than Medicare payments to hospitals, as used by
Kessler and McClellan, Sloan et al. used total inflation-adjusted Medicare payments in
order to include outpatient care. They used 15 years of data (compared to Kessler and
McClellan’s three), and they expanded upon Kessler and McClellan’s list of medical
diagnoses. They found no reduction in inpatient medical expenditures and that both direct
and indirect reforms reduce payments for AMI or ischemic heart disease hospital care,
with no effect for other outcomes studied, and neither direct nor indirect tort reforms
effected survival probability, thus no evidence for defensive medicine.
Among studies using changes in tort law to examine defensive medicine, those
that have found an effect have more often found an effect of damages caps than other tort
34
reforms. Currie et al. (106) reported that reform of the joint and several liability rule
reduced complications of labor and procedure use, while caps on non-economic damages
increased complications of labor and procedure use, and Yang et al. (107) reported that
caps on non-economic damages increased VBAC rates and decreased cesarean rates, the
effect increasing with the stringency of cap. Kilgore et al. (106) estimated the effects of
changes in state tort law on malpractice premiums, rather than defensive medicine, and
reported a dose-response effect of inflation-adjusted damage caps. We hypothesize that,
similarly, a dose-response effect of damage caps on defensive medicine exists.
Studies evaluating the association between tort reform and defensive medicine
have used several sources of data on tort reforms. Currie et al. opined that studies of tort
reform and cesarean section may have shown mixed results because some have relied on
flawed information with respect to tort reforms.(108) Avraham found that existing
compilations contained omissions and miscoding (109) and developed a compilation, first
made available in 2006, (110) cross-referencing his own review of tort reform legislation
and court cases with existing tort reform compilations. The recent study by Yang et al.
(107) created a new compilation from several sources that was confirmed for accuracy
with the Avraham database. (110) The present study uses data on malpractice tort reform
from a recently completed Robert Wood Johnson Foundation (RWJF) project that
reviewed all state laws and court decisions for the 1975-2004 period, identifying the
elements of the reforms and their effective dates. This compilation has also been used by
Sloan et al. (104) and by Kilgore et al. (111)
The effects of ten tort reform variables will be examined in this study. Literature
on the association between tort reform and medical outcomes has investigated nine
35
separate tort reforms, and the tort reform database that will be used in this study includes
data on eight of these nine reforms. Several studies have combined reforms into two
groups, direct reforms, which limit the amount that can be recovered in a malpractice
action, and indirect reforms, which operate primarily by providing disincentives to file
suit. (102, 104) Studies have largely analyzed these reforms according to whether a
particular reform is present or absent. Currie et al. (108) criticize the categorization of
reforms into direct and indirect, suggesting that this strategy may reduce any observed
effect, as some reforms work in opposite directions; however, Sloan et al. (104) reported
that results of reforms considered separately were difficult to interpret due to
multicollinearity among reforms. In the present study, reforms were analyzed
individually and combined as direct and indirect.
Literature on Defensive Medicine in Obstetrics
It has long been speculated that the increasing rate of cesarean delivery and the
wide variation in rates in the U.S. are related to defensive medicine. However, the
research has been limited and conflicting. The majority of these studies have examined
the effect of increasing medical malpractice insurance premiums, (94, 95, 98, 105, 107)
or the effect of medical negligence claims experience (96, 97, 100, 112) on cesarean
section rates. Two studies have looked at the effect of tort reform on cesarean (Currie et
al. Yang et al. 2009). (106, 107) and one looked at the effect of malpractice premiums
on cesarean while using tort reform as an instrumental variable (Dubay 1999). (105)
Yang et al. (107) observed VBAC rates significantly higher and cesarean delivery
rates significantly lower in states with caps on noneconomic damages and found no effect
of other tort reforms. Currie et al. (106) found that induction and stimulation of labor,
36
cesarean delivery, and complications of labor were significantly decreased in the
presence of joint-and-several liability reform while in the presence of damages caps,
each were increased. Few studies examining validity of birth certificate data elements
have included induction and stimulation of labor; however, two state-level analyses
reported poor sensitivity for these two variables, one reporting 71.7% sensitivity for a
combined “induction or augmentation” variable (113) and the other 42.5% for induction
and 25.7% for stimulation. (114) Poor sensitivity is also reported among labor
complications variables. (113, 115, 116) Findings by Currie et al. of opposite effects of
two tort reforms on these variables are therefore difficult to interpret.
Studies of malpractice insurance premiums on cesarean delivery rates have
consistently found statistically significant associations between liability premiums and
cesarean delivery rates. (94, 95, 98, 105, 107) Among those examining the effect of
medical negligence claims experience, Grant et al. (112) found that physicians
experiencing high payout claims increased cesarean rates by 1%, while others have found
no effect of claims experience on cesarean rates. (96, 100, 117) Generally, studies of tort
reform have had mixed results, while studies of malpractice premiums have found an
association with cesarean delivery rates and studies of claims experience have not.
The most recent paper to examine the effects of liability reform on obstetric
practice (Yang et al.) (107) used data from Medical Liability Monitor Annual Rate
Survey and from National Center for Health Statistics (NCHS) Natality Detail file. They
found effects of non-economic damage caps on VBAC and cesarean and found an effect
of pretrial screening on VBAC but no significant associations for other reforms.
37
Gaps in the Literature
Despite several studies examining malpractice premiums and cesarean delivery
and tort reform and cesarean delivery, there are several remaining gaps in the literature
that this work is intended to fill. This study uses nationwide data, covers a greater span
of years (14) than the majority of prior studies and includes more recent data (1991-
2004). Many of the older studies of tort reform and cesarean delivery used unreliable
sources of tort reform data. This study will use a recent, thorough, and detailed
compilation that includes information on damage cap levels.
Studies using birth certificate data to examine cesarean delivery in the context of
defensive medicine have included maternal medical history and complications of labor
and delivery variables from the birth certificate in their analyses to control for underlying
medical risk. (37, 95, 96, 105-107, 118) Birth certificate data elements are subject to
varying degrees of reliability and validity. Validation studies have found concordance
between birth certificates and hospital discharge data, as well as sensitivity and positive
predictive value for method of delivery (vaginal versus cesarean) to be nearly 100%;
however, reliability of data elements for some maternal risk factors and complications is
fair to poor. (115) These data are useful for many types of comparisons, such as
monitoring trends in complications over time but some of these variables are not suitable
for inclusion in the models used for this study. The models include only those variables
shown by validity studies to have a high degree of sensitivity, and the outcome of interest
is total cesarean deliveries. VBAC and primary versus repeat cesarean are important
outcomes but not well-captured by the birth certificate data. Justification for inclusion or
exclusion of each variable is discussed in Chapter 3.
38
A recent study (Yang 2009) (107) has explored the effects of tort reforms on
obstetrical outcomes. The present study differed from that of Yang et al. in several ways.
The outcomes explored by Yang include VBAC, primary cesarean and total cesarean.
When births are categorized as vaginal versus cesarean, reliability has been found to be
very high; (115, 119) however, poor sensitivity has been reported for VBAC (115, 116,
119) and for primary cesarean and repeat cesarean. (116) Thus, this analysis categorized
delivery method as cesarean versus vaginal only. The natality dataset contains no reliable
mechanism for linking multiple births to one delivery event. In order to avoid the
possibility of over-counting cesarean births, this study examines singleton births only.
Yang controlled for 14 clinical risk factors for cesarean, addressing the high level of
colinearity by collapsing them into 4 principle components. This analysis includes four
of those 14 risk factors that are of reportedly high reliability, and they are included as
individual-level variables. Yang also adjusts for obesity and insurance status, using state-
level data. Rather than employing a mixed effects model and adjusting for various state-
level factors, this analysis controls for factors varying among states via fixed effects
modeling.
This study investigated whether there is a dose-response effect between damage
caps and cesarean delivery rates for both caps on non-economic damages and caps on
punitive damages. Four levels were examined for each cap (<$250,000, $250,000 to
<$500,000, $500,000 to < $750,000, and > $750,000). Yang et al. also investigated the
effect of damage caps on delivery methods, examining three levels of caps on non-
economic damages (< $250,000, $250,001 - $500,000, and > $500,000). The cap
39
variable was also modeled as a dichotomous yes/no variable and as a continuous variable
to examine differences in effect.
Studies of the effect either of malpractice premiums or tort reforms have not
considered whether the effect on cesarean delivery rates differs by race, marital status and
maternal educational attainment. There is, however, strong evidence that these factors
plus socioeconomic status affect the likelihood of undergoing a cesarean. (120, 121)
Also, Dubay et al. found the effect of malpractice premiums on cesarean rates and birth
outcomes to differ by maternal marital status and educational level. (105)
This work contains several new elements and, through methodological
refinements and other subtle improvements, builds on the work of others to inform the
ongoing debate on the existence of defensive medicine. This study takes advantage of
the richness of national birth certificate information as a data source while recognizing
and accounting for its limitations. Additionally, a multi-disciplinary approach brings new
perspective to the analysis and to interpretation of the findings.
40
Table 2. Key Defensive Medicine Literature
Authors Outcome Data Sources Years Geography Key Findings Rock 1988 (94) Malpractice
premiums Cesarean -Hospitals (NY)
-Dept. of Public Health (IL)
1981, 1983 New York Illinois
Statistically significant correlation between differences in cesarean section rates and differences in liability premiums for insurance territories within both New York and Illinois.
Localio 1993 (95) -Malpractice premiums
-Perceived risk of claim
-Rates of paid claims
Cesarean Hospital discharge data
1984 New York Malpractice premiums and physician perceived risk of suit associated positively with cesarean. No significant association between cesarean and physician claims history.
Baldwin 1995 (96) Malpractice claims
experience and exposure
-Obstetric ultrasound use -Referral and consultation -Prenatal care use -Cesarean
-Physician survey -Chart review -insurance databases
9/88-8/89 Washington No statistically significant association found for any of the outcome measures.
Kessler, McClellan 1996 (102)
Tort reforms Serious heart disease (hospital expenditures, mortality, and complications)
-Medicare data -Tort reform compilation
1984,1987,1990
United States -Direct tort reforms associated with reduced hospital expenditures of 5-9% within 3-5 years of adoption. -Indirect tort reforms not associated with expenditures or health outcomes. -Neither direct nor indirect reforms associated with differences in mortality or complications.
Tussing 1997 (118) Malpractice lawsuits
Use of EFM* Fetal distress Cesarean
-Vital records -Hospital discharge data
1986 New York Malpractice exposure is associated with each of the outcomes.
41
Table 2. Key Defensive Medicine Literature
Authors Outcome Data Sources Years Geography Key Findings Dubay 1999 (105) -Malpractice
premiums -Tort reforms
-Cesarean -Apgar
NCHS natality data 1990-1992 United States - Cesarean section rates increase in response to increased malpractice premiums. - Higher premiums do not lead to improved 5-minuteApgar scores. -Among mothers of lower SES, decrease in Apgar scores in response to higher premiums
Dubay 2001 (99) -Malpractice premiums -Malpractice liability concerns
-Prenatal care utilization -Low birthweight -Low Apgar
NCHS natality data 1990-92 United States -Increases in malpractice premiums associated with later initiation of prenatal care and fewer prenatal care visits. -No association with low birthweight or low Apgar.
Grant 2004 (112) Malpractice claims
Cesarean -Hospital discharge data - Insurance claims data
1992-1995 Florida Physicians experiencing high payout claims increased cesarean rates by 1%.
Currie 2008(106) Tort reforms Induction and stimulation of labor, cesarean and complications of labor and delivery.
-Compilation of tort reforms -NCHS natality data, 10% random sample
1989-2001 United States Joint and several liability reform significantly reduced and damage caps increased probability of cesarean.
Kilgore 2006 (111) Tort reforms Malpractice premiums
-Compilation of tort reforms -Medical Liability onitor -Area Resource File
1991-2004
United States Damage caps and statutes of repose associated with reduction in premiums.
42
Table 2. Key Defensive Medicine Literature
Authors Outcome Data Sources Years Geography Key Findings Baicker 2005 (98) -Payment on
claims -Malpractice liability -Malpractice premiums
-Malpractice premiums -Physician workforce -Cesarean, six other medical procedures -Medicare expenditures
-Medical Liability Monitor -National Practitioners Data Bank -Area Resource File -NCHS -Dartmouth Atlas of Healthcare
Payments: 1992-94, 2000-02 Premiums: 1992-93, 2001-02 Physician data: 1989 , 1995 Treatments: 1992-93, 1998-2001
United States -Malpractice payments did not affect premiums. -Increases in malpractice costs did not affect the size of the physician workforce. -Increases in malpractice costs did not result in increased use of medical procedures of interest.
Baicker 2006 (37) -Payment on claims -Malpractice premiums
Cesarean -Medical Liability Monitor -National Practitioners Data Bank
-NCHS linked birth and death data
1995-98
198 U.S. counties with populations > 250,000
Counties whose risk-adjusted rates are higher than unadjusted rates have cesarean usage that is more intensive than what would be predicted using observable characteristics. -Average birth through cesarean has a systematically lower predicted probability of cesarean birth in areas that do more cesarean sections.
Kim 2007 (100) Malpractice claims
Cesarean -NCHS natality data National Practitioner Data Bank
1992-98
1990-2005
United States Cesarean rates insensitive to malpractice risk.
Sloan 2009 (104) Tort reforms Serious heart disease (Medicare payments,
National Long-Term Care Survey merged with Medicare claims
1985-2000 United States Neither direct nor indirect reforms had a significant effect on health outcomes.
43
Table 2. Key Defensive Medicine Literature
Authors Outcome Data Sources Years Geography Key Findings survival probability)
and other data
Yang, 2009 (107) -Tort reforms --Malpractice premiums
VBAC c-section repeat c-section
NCHS natality detail file Medical Liability Annual Rate Survey National Conference of State Legislatures, American Tort Reform Association, unnamed internet database
1991-2003
United States VBAC rates significantly higher and c-section rates significantly lower in states with caps on noneconomic damages, effect increased with stringency of cap. No other tort reforms significantly associated with rates of these delivery methods.
*Electronic fetal monitoring.
44
CHAPTER 3
METHODS
Conceptual Framework
Conceptual Framework for investigating the association of tort reform with
cesarean and other delivery methods.
Policy
Direct Tort Reforms Caps on non-economic damages Collateral source offset
Indirect Tort Reforms Caps on contingency fees Periodic payments Modification of joint and several Liability rule Statutes of limitations Statutes of repose
Practice
Cesarean Section
Confounders Maternal characteristics age race Hispanic ethnicity foreign-born education marital status parity diabetes hypertension tobacco use pre-natal care utilization
Fetal characteristics gestational age birthweight non-vertex presentation Unobservable social, legal, political, economic factors that vary by state.
45
Research Questions
1. Are “direct” tort reforms, “indirect” tort reforms or any of seven tort reform measures
associated with changes in rates of cesarean delivery?
Hypothesis 1: The presence of direct tort reforms is associated with a decrease in cesarean delivery rates. Hypothesis 2: The presence of one or more of seven tort reforms is associated with a decrease in cesarean delivery rates. Hypothesis 3: The presence and magnitude of damage caps, alone or in combination with other tort reforms, is associated with a decrease in cesarean delivery rates. Hypothesis 4: There is a dose-response relationship between the level of damage caps and decrease in cesarean delivery rates.
2. Are the effects of “direct” tort reforms, “indirect” tort reforms or any of seven tort
reform measures associated with differential rates of cesarean delivery by race, marital
status or maternal educational attainment as recorded on the infant’s birth certificate?
Hypothesis 1: The effect of tort reforms on cesarean delivery rates differs by the maternal demographic characteristics of race, marital status and educational attainment. For this study, it was necessary to frame the hypotheses in a form testable using
econometric methods. “Other things equal” is economics parlance for an assumption that
everything remains constant except the variables of interest.
Testable hypothesis:
Other things equal, in states that that have adopted certain tort reform
measures, the probability of having a cesarean delivery is lower following
implementation of the reforms
46
Subjects
Included as subjects were all singleton infants born in the United States, 1991-
2004 (n=54,445,327). Although multiple births are known to increase the likelihood of
cesarean delivery, there is no mechanism available, when using birth certificate data, for
linking multiple births to each other as products of the same delivery. To avoid counting
the same delivery multiple times, which may have resulted in over-counting of the
number of cesarean deliveries, this study is limited to singleton births.
Geographic Units of Analysis
This study examined the effect of state tort laws on cesarean delivery rates.
Data Sets Births
The principal data used in these analyses were the U.S. birth certificate data from
the National Center for Health Statistics (NCHS) public use birth files. The United States
Standard Certificate of Birth was modified in 1989 and again in 2003. Although data on
method of delivery was collected on birth certificates beginning in 1989, it was not until
1991 that all states and the District of Columbia were reporting this information. Data
prior to 1991 were therefore not included in the analysis. Data for some variables are not
comparable between the 1989 and 2003 birth certificate revisions. States began adopting
the 2003 Revised Standard Certificate of Live Birth in 2003, and by the end of 2004, it
was in use in nine states. (19 states by 2009), (27) further complicating comparability
across states and years. The public use data files do not contain geographic identifiers for
years after 2004, precluding state-level analyses. The analysis therefore included the
47
years 1991-2004, using bridged and recoded variables when appropriate and excluding
variables that cannot be compared across years.
The birth certificate data files contain information on the state of birth, the method
of delivery, and other variables related to maternal demographic characteristics, maternal
health, infant health, and risk factors associated with the pregnancy and delivery. Among
the maternal risk factors for which data are available are age, education, race, marital
status, parity, plurality, presence of diabetes, hypertension, eclampsia, previous preterm
and low birthweight births, tobacco and alcohol use, and weight gain. Among the fetal
risk factors are gestational age, prenatal care utilization, induction of labor, stimulation of
labor, premature rupture of membranes, precipitous labor, prolonged labor, dysfunctional
labor, breech presentation, and cord prolapse. These variables are subject to varying
levels of reliability and many are exclusive to either the 1989 or the 2003 birth certificate.
Justification for use or omission of each variable is presented below. Variables
considered for inclusion in the fixed effects analysis are presented in Table 3, and those
actually used in the analysis and how they were coded are presented in Table 4.
Tort Reform
A complete compilation of state-by-state reforms for the period 1975 through
2004 were used to examine the impact of tort reform on cesarean delivery. (89, 111) A
team of law students, under the supervision of a law professor, prepared summaries of
tort reform for each state, including statutes and case rulings related to eleven reforms
enacted since 1975. Laws and court actions on eleven tort law provisions were
examined. The database’s coding scheme includes dichotomous variables for most
provisions, number of years for statutes of limitations and repose, and dollar amounts for
48
caps on noneconomic damage awards. The set of codes has been thoroughly documented
and validated, reflecting the tort provisions in effect in each state for each year 1975
through 2004. (111) The variables in the tort reform database and their coding are
presented in Table 4. Damage caps are coded according to levels. All other tort variables
are coded as absent or present (0/1).
Variables
Each tort reform and birth certificate variable employed by investigators
conducting similar research was examined for possible inclusion in our analyses (Table
3). This section first addresses variables selected for inclusion in the analyses, followed
by discussion of excluded variables and by discussion of unobserved and unmeasurable
confounding variables. Tables 3 and 4 list the variables addressed by this discussion.
Dependent variable Cesarean delivery: Cesarean delivery is the primary outcome to be examined, as the
purpose of the study is to examine whether cesarean rates change in response to tort
reform. Twelve of the papers presented in Table 2 included cesarean delivery among the
outcome variables. (37, 100), (94-96), (98), (99), (105, 106, 112, 118) Six of these
papers, those by Dubay et al., (99, 105) by Currie et al., (106) by Baicker et al., (37, 98)
and by Yang et al. (107) used NCHS natality data, with the others employing other data
sources. Among the studies using NCHS data to examine delivery method as an outcome
measure, Dubay, Currie, and Kim used cesarean only, while Yang also looked at VBAC
and primary cesarean delivery. When births are categorized as vaginal versus cesarean,
sensitivity has been found to be very high; (115, 119) however, poor sensitivity has been
reported for VBAC (115, 116, 119) and for primary cesarean and repeat cesarean. (116)
49
Recording of a delivery as primary, repeat or VBAC is likely poor, because it requires
knowledge of prior deliveries, whereas recording a delivery of vaginal versus cesarean
requires knowledge only of the current delivery.) Thus, for the present analysis, delivery
method is categorized as cesarean versus vaginal only (Table 4).
Independent Variables
Tort reforms adopted by states include caps on non-economic damages, caps on
or elimination of punitive damage awards, elimination of mandatory prejudgment interest
(interest accrued between the date of injury and entry of the judgment), collateral source
offset, caps on contingency fees, periodic payments, modification of joint and several
liability rule, patient compensation fund, statutes of limitations/repose, pre-trial
screening, and mandatory pre-judgment interest. These terms are explained in the
discussion which follows. Pre-trial screening was not included in this analysis, because
no changes were made during the study period. Elimination of mandatory prejudgment
interest was not included, because this information is not included in the database of tort
reforms used for this project.
The effects of nine tort reform variables will be examined in this study, consisting
of seven reforms and two variables that group the seven reforms as either direct or
indirect. Caps were coded as absent or present (0/1) and in a series of levels. Other tort
reforms were coded as absent or present (0, fraction of year reform was in effect) in each
of the 14 years under study.
Several studies examining the effects of tort reform on medical outcomes have
incorporated a “lag time” into their analysis (105, 107) on the supposition that there
would be a delay from the time legislation is enacted until this legislation is reflected in
50
changes in clinical practice. It should be noted that Dubay et al.’s use of a lagged analysis
was to account for the delay in tort reforms impacting insurance premiums, rather than
medical practice. (105) Currie et al. did not employ a lagged analysis in the belief that
tort reforms would affect the filing of lawsuits without a lag, whereas there would be a
lag in the effect of tort reforms on premiums.(106) Sloan et al. have reported that
physicians are generally aware of tort reforms prior to their implementation, (122, 123)
likely via news outlets, professional organizations, and colleagues. Their defensive
response, if any, would therefore likely take effect immediately. Using this rationale,
lagged analysis was not employed in the present study. Tort reforms to be included as
independent variables are caps on non-economic damages, collateral source offset, caps
on contingency fees, periodic payments, modification of joint and several liability rule,
patient compensation fund, statutes of limitations/repose. Additionally, these seven
reforms were grouped into two categories, direct tort reforms (caps on non-economic
damages, collateral source offset) and indirect tort reforms (caps on contingency fees,
periodic payments, modification of the joint and several liability rule, patient
compensation fund, and statutes of limitations/repose). These nine variables are
operationalized as presented in Table 4.
Direct Tort Reforms: This variable groups reforms that directly limit the amount of
recovery. This includes caps on non-economic damages and, and collateral source offset.
Others have also included caps on or elimination of punitive damages in this category.
(102, 107, 123)
Indirect Tort Reforms: This variable groups reforms with an indirect effect on reducing
awards by providing disincentives to file suit: caps on contingency fees, periodic
51
payments, modification of the joint and several liability rule, patient compensation fund,
and statutes of limitations/repose.
Caps on non-economic damages: Caps on non-economic damages limit recovery for
pain and suffering, which is often sought in addition to compensation for economic
damages, which are monetary losses, such as medical expenses and lost wages. Several
researchers examining defensive medicine and tort reform have included non-economic
damages caps as either present or absent, (102, 105, 106, 123), while Kilgore et al. (111)
and Yang et al., (107) examined cap levels. In this analysis, caps are categorized as <
250,000, > $250,000 and < 500,000, > $500,000 and < 750,000, and > $750,000. Caps
will also be coded as a dichotomous (yes/no) variable and a continuous variable in
alternate model specifications.
Non-economic damages caps were adjusted to year 2004 dollars. For example,
throughout the study period, California had in place a $250,000 cap on non-economic
damages. Due to inflation, the purchasing power of a dollar decreases each year, so that
$250,000 cap in 2004 would have been worth $344,347 in 1991, $281,513 in 1997 and so
on. This adjustment of the cap amount more accurately reflects its effect on damages
awards than using the flat statutory cap amount. Some states include a provision for
inflation in their statutory cap.
Modification of the joint and several liability rule: The joint and several liability rule
defines the way in which liability is apportioned among defendants. Modification of the
rule is intended to deter filing of lawsuits by preventing assignment of a larger share of
liability to a “deep pocket” defendant. Currie et al. reported a finding that JSL reduced
the effect of preventable complications of labor and delivery.
52
Collateral source offset: A collateral source offset requires the plaintiff to disclose
amounts received from collateral sources (e.g., medical insurance, disability payments),
and economic damages are offset by this amount. The intent is to prevent “double
dipping.”
Caps on contingency fees: Limiting attorneys’ fees reduces profitability and thus the
likelihood of filing suit.
Periodic payment provisions: This reform adds a requirement that payment of a
judgment for future damages be paid over time in the form of an annuity, rather than as a
lump sum.
Statutes of Limitations and Repose: Changing the time limits for filing suits presumably
reduces the number of claims filed. Both statutes of limitations and statutes of repose are
time limits beyond which legal action cannot be brought. In most states, the time limit
specified for a statute of limitations is counted from the date the plaintiff discovered or
should have discovered that an injury occurred (often but not always the actual date of
injury). The justification for statutes of limitations is that there should be point in time
when a potential defendant no longer needs to worry about being sued.(69) A statute of
repose differs from a statute of limitations in that the time limit it imposes is tied to some
event other than an injury (e.g., date of construction, date of manufacture, date of
treatment) and may run out before an injury occurs. For example, a woman in Florida
who had received a blood transfusion in 1986 learned in 1990 that she had contracted
HIV infection; however, the discovery date was beyond Florida’s four-year statute of
repose, and legal action was barred. (124)
53
Confounders
The association between tort reform and choice of delivery method is potentially
confounded by maternal demographic characteristics, maternal risk factors, labor and
delivery complications, fetal characteristics, and a variety of social, legal, political, and
economic factors that vary with geography .A number of maternal demographic
characteristics, maternal risk factors, labor and delivery complications, and fetal
characteristics are captured by the birth certificate data; however, among them are
variables that are subject to significant under-reporting. In order to avoid introducing
bias, variables with poor reliability were excluded from the analysis. Studies have shown
some variables to be of poor or moderate reliability, with sensitivity for some labor and
delivery complications of 30% or less. Other studies have suggested that this
underreporting may be differential according to maternal characteristics (e.g., unwed
mother, low educational attainment, Hispanic ethnicity) for some variables (116, 125,
126) or characteristics of the pregnancy or birth (e.g., preterm birth, birth injury). (127)
Other researchers addressing similar questions have included many or most of the
birth certificate variables in their models without considering the impact of data quality.
The discussion below explains why we believe it is appropriate or inappropriate to
include each variable in the models used in the present study. The final list of
confounders consists of the maternal characteristics of age, race, education, marital
status, diabetes, hypertension, tobacco use, pre-natal care utilization and the fetal
characteristics of gestational age, birthweight, and non-vertex presentation. Several
important predictors of cesarean delivery that are not recorded on the birth certificate, and
54
hence not included in this analysis, are measures of socio-economic status, insurance
status and type of insurance.
Confounders that are unknown or cannot be measured, “unobserved” but fixed
confounders, were accounted for via fixed effects modeling. Kessler et al., while using
fixed effects modeling, controlled separately for several time-varying state-specific
covariates, including the political party of each state’s governor, the majority political
party of each house of each state’s legislatures, and lawyers per capita. (102) These
variables were not added, as adequate control was achieved via fixed effects modeling.
Maternal Demographic Characteristics
We examined rates of cesarean delivery by maternal race and ethnicity, marital
status and educational attainment, because rates of cesarean delivery differ according to
each of these factors. (128) Most demographic variables are considered to be very
reliably reported in the birth certificate data. (18) Dubay et al. found that higher
malpractice claims risk results in increased use of cesarean section among unmarried
women with less than a high school education, which she used as a measure of SES, as
marital status and education are often correlated with income and insurance coverage.
(105)
Maternal Race: Cesarean rates vary by race and are highest for non-Hispanic black
women, (18) Several studies of defensive medicine and cesarean delivery have
controlled for race as a dichotomous Black and Other variable. (105-107) None have
separately stratified by race and ethnicity. The 2003 revision of the U.S. Standard Birth
Certificate uses an expanded classification scheme for race that includes multiple race
categories; however, data for states using the new categories has been bridged to single
55
race categories to facilitate comparability among states. For the present analyses, race
was categorized as White, Black, Native American, and Asian.
Hispanic ethnicity of mother: The cesarean rate has increased over time among all racial
and ethnic subpopulations, including Hispanic women. (19, 129) Hispanic ethnicity was
coded as yes/no.
Foreign-born mother: Dubay et al. (105) controlled for foreign birth of the mother in
their study of the effect of malpractice premiums on cesarean section rates. Literature is
sparse on the effect of foreign birth on cesarean; however, two studies report higher rates
of cesarean delivery among foreign-born mothers. Forma et al., (130) in a study of 50,000
deliveries at Grady Memorial Hospital in Atlanta, found a higher rate of cesarean
delivery among foreign-born women from Africa but not for foreign-born women overall,
and a study of Latina women in San Diego found that foreign-born primiparas (women
experiencing a first birth) were twice as likely to have undergone a cesarean as their U.S.-
born counterparts. (131)
Maternal Age: Pregnancy risk is increased at either end of the age spectrum. Births to
older women and to very young women have become more common during the time
period under study. Cesarean rates have been shown to increase with maternal age. (61)
Among the contributing factors may be the association of dystocia with increasing
maternal age. (42) In 2007, the cesarean rate for mothers aged 40–54 years in 2007 was
more than twice the rate for mothers under age 20 (48% and 23%, respectively).(132)
For this analyses, maternal age was categorized as <20, 20-24, 25-29 30-34, 35-39, 45-
54, consistent with categories used by Menacker et al. (132)
56
Maternal Education: Cesarean rates have been shown to increase with increasing
educational attainment. (18) Data on maternal educational attainment are not considered
comparable across birth certificate revisions, as the 2003 Certificate asks for the highest
degree or level of school completed (e.g., high school diploma, some college credit but
no degree, bachelor’s degree) and the 1989 Certificate asks for the highest grade of
school completed (years of grade school, years of high school or years of college).
Variables were re-coded to form three categories of educational attainment based roughly
on the work of Dubay et al. (1999), 0-11 years, 12 -15 years, and four or more years of
college.
Including adolescents in these educational categories produces misleading results,
as persons under 19 years of age have not had the same opportunity to complete
schooling as an adult. Mothers in this younger age group represent 10.4% of all births
(2006 data). Some studies have excluded adolescents to avoid this comparability
problem; however, most do not account for it. Studies focusing on adolescents have used
an “education for age” approach; (133) however, there appears to be little support for
such a strategy across age groups. This analysis includes adolescents, and, consistent
with other reports based on NCHS birth data, (31) make no special provision for years of
education for age.
Marital Status: Associations have been reported for unmarried status and low birth
weight, preterm birth, and small for gestational age birth. (134) Dubay et al. (105) used
mother’s marital status and educational attainment as proxies for socioeconomic status.
Currie et al. (106) and Baicker et al. (37) also controlled for marital status in their
57
analyses. The present analysis included marital status as a dichotomous variable,
unmarried, married.
Plurality: Multiple gestation pregnancies are more likely to be delivered via cesarean;
however, birth certificate data do not allow the linking of multiple births to the same
delivery event. The 2003 revision of the U.S. Standard Birth Certificate includes a
matching number for plural births. The present analysis includes the years 1991-2004,
and by the end of 2004 just nine states had adopted the new birth certificate. The analysis
is limited to singleton deliveries to avoid potentially over-counting of the number of
cesarean deliveries and because single and multiple births differ in the types of medical
complications they experience. Among studies using birth certificate data to examine
defensive medicine and cesarean delivery, Dubay et al.(105) limited their analysis to
singleton births and Currie et al. (106) and Yang et al. included multiple births,
controlling for them in the analysis. (107) Baicker et al. (37) did not address plurality.
Kim (135) performed a separate sub-analysis of multiple births but did not account for
them in the main analysis. Multiple births were excluded from this analysis.
Maternal Medical History
Several maternal medical history variables included by other researchers in their
analyses were not included in the present analysis, primarily because validation studies
report poor reliability. Variables included in the analyses are discussed below. Variables
used by others but excluded from this analysis are presented in a separate section.
Included and excluded variables are listed in Tables 3 and 4.
58
Parity: Associations have been reported between the number of times a woman has given
birth and certain obstetric complications. Some of these complications, such as
preeclampsia (136) and dystocia (42) are more common in nulliparous women, whereas
others, such as placenta previa (137) are more common in multiparous women. Overall, a
first birth carries a higher risk of complications and of cesarean delivery. Among papers
examining defensive medicine and cesarean, only Currie et al. controlled for parity in
their analysis. The present analysis includes parity as a dichotomous variable,
(primiparous/multiparous). The term “primiparous,” rather than “nulliparous” is used
because the analysis uses birth certificate data, which was collected following the birth.
During labor and delivery, the same woman would be correctly described as nulliparous.
Maternal Tobacco Use: Smoking during pregnancy increases the risk of pregnancy
complications, including premature rupture of membranes, abruptio placenta, and
placenta previa, as well as increasing the risk of delivering a premature and/or low
birthweight infant. Infants born to mothers who smoke during pregnancy have about
30% higher odds of being born prematurely than infants born to mothers who do not
smoke. (138) Maternal tobacco use is of moderate sensitivity.(115, 125) This was coded
as a dichotomous (yes/no) variable.
Diabetes: Diabetes is a chronic metabolic disorder characterized by insulin deficiency,
which results in elevated blood sugar (hyperglycemia). Glucose transported across the
placenta puts the fetus at risk for intra-uterine hyperglycemia, (139) hypoglycemia, or
other metabolic disturbances. (140) The fetus’s responds to maternal diabetes with
increased insulin production and accelerated fetal metabolism, which can result in excess
fetal growth and macrosomia (gestational weight > 4,000 grams). Macrosomia increases
59
the risk of shoulder dystocia (impeded delivery of the shoulders often accompanied by
nerve injury), clavicle fracture, and other birth injuries. (140) Prophylactic cesarean has
been recommended when fetal weight is estimated at 4,500 grams or more. (140)
Diabetes is associated with chronic and gestational hypertension (140) and with obesity.
(141) For this analysis, diabetes is a combined variable including both pre-pregnancy
(chronic) and gestational diabetes and was coded as a dichotomous (yes/no) variable.
Hypertension: Hypertension, although not a direct indication for cesarean, may co-occur
with other risk factors, such as obesity, and may be a precursor to more serious
pregnancy complications. Preeclampsia is the development of hypertension plus
proteinuria or generalized edema during pregnancy and may progress to eclampsia, which
is characterized by convulsions. Hypertension increases the risk of abruptio placenta and
of fetal growth retardation and intrauterine death, (13) and pregnancy-induced
hypertension is among the leading causes of maternal mortality. (3)
Pre-pregnancy (chronic) was coded as a dichotomous (yes/no) variable.
Gestational was coded as a dichotomous (yes/no) variable.
Adequacy of Prenatal Care: Adequacy of prenatal care will be measured via the Revised
Graduated Index of Prenatal Care Utilization (R-GINDEX) proposed by Alexander and
Kotelchuck. (142) The R-GINDEX is a graduated index using six categories of care
(intensive, adequate, intermediate, inadequate, no-care, and missing/unknown), that
improves upon on the Graduated Index of Prenatal Care Utilization (GINDEX) described
by Alexander and Cornely. (143) Early indices, such as the Kessner Index and the
GINDEX rely on a 1972 Institute of Medicine Report and are considered flawed, while
more recently developed indices, such as the Adequacy of Prenatal Care Utilization
60
(APCNU) index and R-GINDEX, incorporate 1989 ACOG prenatal care
recommendations and are thought to better reflect adequacy of care. (143)
These categories were used for the descriptive analysis. For the fixed effects analysis, the
inadequate and no care categories were combined and a dichotomous (yes/no)
“inadequate or no care” variable was created. Baicker et al. included prenatal care use in
the index of patient-level characteristics developed for use in their models, using the
Kessner index (adequate, intermediate, or inadequate). Kim (100) examines prenatal care
as an outcome, evaluating the effect of malpractice risk on the number of visits (not
accounting for gestational age at birth).
Labor and Delivery Characteristics
Many labor and delivery variables included by other researchers in their analyses
were not included in the present analysis, primarily because validation studies report poor
reliability. Variables included in the analyses are discussed below. Variables used by
others but excluded from this analysis are presented in a separate section.
Non-vertex presentation: ACOG’s 2006 opinion on delivery of a term singleton breech
birth was that a decision to attempt vaginal delivery should depend on the experience of
the health care provider, acknowledging that cesarean delivery be the preferred delivery
mode for most physicians. (144) This is a departure from the 2002 opinion that patients
with a singleton in persistent breech presentation or a second twin in non-vertex
presentation should undergo a planned cesarean. (145) Cesarean is the method of
delivery for 85% of breech births. On the 1989 revision of the U.S. Standard Birth
Certificate, presentation is categorized as vertex, breech, or other malpresentation. The
61
2003 birth certificate classifies all malpresentations as non-vertex. For this analysis,
breech and other malpresentation have been combined to allow comparability. Among
labor and delivery characteristics, only non-vertex presentation is sufficiently reliable for
inclusion in the analysis. The following variables are therefore excluded from the
analysis due to poor, (115) (125) and possibly differential, reporting. Non-vertex
presentation was recorded for 3.18% of singleton births 1991-2002 (12.9% of cesarean
deliveries) and has been constant over time.
Infant Characteristics
Gestational Age: In 2005, 46.8% of singleton births of less than 32 weeks gestation were
delivered via cesarean. (61) For this analyses, gestational age was categorized as < 32
weeks (extremely premature), > 32 weeks, < 36 (premature), > 37 weeks and < 41
weeks (normal), and > 41 weeks (postmature). Gestational age was based on last
menstrual and period, rather than clinical gestational age. Wingate et al., (146) using
NCHS natality files for 2000-2002, found perfect agreement between last menstrual
period and the clinical estimate for just 53.8-57.0% (differing according to demographic
characteristics) of records. The last menstrual period measure is reportedly less subject to
systematic error and is therefore preferable for use in population-based analyses. (146)
Wingate et al. also reported that the greatest discordance between last menstrual period
estimate and clinical estimate occurred at 32–33-weeks’ gestation, and the
proportion of cases with their clinical estimates of gestational age two or more weeks
higher than the last menstrual period estimate was greatest between 32 and
62
35 weeks. (146) As pre-term birth is defined as birth at less than 37-weeks’ gestation, use
of the clinical estimate could result in a substantial under-estimate of the number of pre-
term births, affecting our ability to control for pre-term birth in the analysis.
Birthweight: The association between low birthweight and cesarean delivery is well-
recognized; however, high birthweight infants are also often delivered via cesarean.
Other factors associated with macrosomia include a previous infant > 4,000 g and post-
maturity. Over time, there has been an increased tendency toward larger babies (in the
presence or absence of obesity and diabetes) (51) (147) Boulet et al. (2005) report that
rates for cesarean delivery of macrosomic infants showed a pattern of increase between
1989 and 2000. (148) Boulet et al. (2003) also report that 25.5% of infants weighing
4,000 -4,499 grams , 35.6% of infants weighing 4,500-4,999, and 50.6% of infants
weighing in excess of 5,000 grams were delivered via cesarean while the percentage of
normal weight (300—3999 grams) infants delivered via cesarean during the same period
was 18.0%. (149) For these analyses, birthweight was categorized as < 2500 g (LBW),
> 2500 but < 4000 (normal birthweight), and > 4000 (high birthweight).
Table 4 presents the variables selected for inclusion in the analysis and describes
how they will be operationalized. The confounders for which we will adjust are the
maternal characteristics of age, race, education, marital status, parity, diabetes,
hypertension, tobacco use, pre-natal care utilization and the fetal characteristics of
gestational age, birthweight, and non-vertex presentation. The “NCHS Variable Name”
column lists the variables from the NCHS public use natality datasets from which our
variables were derived. The analysis uses data from fourteen NCHS datasets from the
years 1991-2004. During the earlier years, the 1989 revision of the U.S. Standard Birth
63
Certificate was in use. The birth certificate was revised in 2003. Just a few states adopted
the new certificate in 2003, and it came into use in additional states in 2004. As a result,
during 2003 and 2004 states were using two different versions of the birth certificate. The
2003 and 2004 datasets include sets of variables for both revisions. Most variables
included in the dataset used for this analysis were re-coded from multiple variables to
allow comparability among states and across years.
Excluded Variables
The following section describes variables excluded from the analysis, with
reasons for exclusion provided. This section is provided to explain why variables used in
similar research were excluded from the present analysis. Table 3 lists variables included
and excluded from the analysis.
Tort Reform Variables
Two tort reforms included by some other researchers were excluded from this analysis.
Caps on or elimination of punitive damages awards: These caps place limits on awards
intended to punish a defendant for willful egregious conduct. Punitive damages are most
often awarded in contract and intentional tort cases and rarely in medical malpractice
actions. (150) Because this reform is rarely adopted by states and is not included in the
database used this study; it was not considered in this analysis.
Patient compensation funds: A patient compensation fund is a state-sponsored excess
insurance pool for medical malpractice liability, often financed via a tax on malpractice
64
insurance premiums, which pays for judgments or settlements in excess of an amount
specified by statute. This reform is not included in the database used for this study.
Birth Certificate Variables
Weekend birth: Patterns of birth by day of week and delivery method have not been
well-described in the literature. Goodman et al., however, report that weekend births,
Sunday more so than Saturday, have shown a progressive decrease since the 1950’s and
opine that this decrease may be related to increasing use of cesarean delivery. (151)
Martin et al. report that, based on U.S. birth certificate data, the average number of births
by day of the week is lower on Saturday and Sunday than for weekdays for both vaginal
and cesarean births. Weekend cesarean births showed a pattern of decrease between
1990 and 2006. (19) Dubay et al. (105) controlled for weekend birth in their analysis.
Others using birth certificate data to examine cesarean delivery in the context of
defensive medicine have not considered day of the week. This variable was included in
the descriptive analysis but not in the tort reform analysis.
The following maternal medical history and labor and delivery complications
variables were excluded from the fixed effects analysis, because of poor reliability.
Studies have reported low sensitivity (<40%) for incompetent cervix and extremely low
sensitivity (< 20%) for eclampsia, previous infant 4000 + grams, previous preterm or
small for gestational age infant in the birth certificate data (115), (125). Dubay et
al.(105) controlled for eclampsia (percent in each county with eclampsia recorded as a
complication on the birth certificate). Baicker et al. (37) included indicators for the
presence of each medical risk factor variables from the birth certificate in an index of
65
characteristics, which was used as a control variable in their models. Currie et al. (106)
included each of these variables in their “high risk” categorization for identifying
preventable and unpreventable cesareans. These four variables were among the 14
collapsed into four principle components by Yang et al. (107) to control for clinical risk
factors for cesarean in their analysis.
Maternal Alcohol Use: Alcohol use during pregnancy is associated with fetal alcohol
syndrome and several types of birth defects.(106) Because of its association with
premature birth, it is a risk factor for cesarean delivery. Sensitivity of maternal alcohol
consumption during pregnancy recorded in birth certificate data has been reported as less
than 25% (115) and will be excluded from this analysis.
Incompetent cervix: Incompetent cervix is a condition that occurs when the cervix begins
to open early in pregnancy in response to pressure from the developing fetus. The
condition may result in premature birth or fetal loss. Treatment may entail use of a suture
to hold the cervix, which is removed late in pregnancy. Among singleton births 1991-
2002, incompetent cervix was recorded on 0.23% of birth certificates.
Eclampsia: Eclampsia (formerly known as “toxemia”) is a life-threatening condition
characterized by seizures and accompanied by high blood pressure. Eclampsia may be
associated with diabetes, high blood pressure, or kidney disease and may result in
abruptio placenta. (152) Eclampsia was recorded for 0.31% of singleton births 1991-
2002.
Previous preterm or small for gestational age infant: Birth of a preterm or small for
gestational age infant is a risk factor for birth of subsequent preterm or small for
66
gestational age infants. (12) This history was recorded for 1.14 % of singleton births
1991-2002.
Previous infant 4000 + grams: Birth of a macrosomic infant is a risk factor for
subsequent macrosomic infants. (149) History of a prior macrosomic infant was recorded
for 1.04% of singleton births 1991-2002.
Dystocia: Dystocia (dysfunctional labor) can result from abnormalities of the expulsive
forces, of fetal presentation, positioning or development, of the maternal pelvis or of the
maternal soft tissues. (12) Dystocia is the most commonly reported indication (43%-70%)
for cesarean delivery (35, 43); however, studies have reported less than 20% sensitivity
for this birth certificate variable. There is broad agreement that dystocia is over-
diagnosed, but the reasons are unclear. Variability in diagnostic criteria, diagnosis made
without an adequate trial of labor, failure to utilize oxytocin stimulation for slow labor,
and fear of litigation are among the hypothesized reasons. (12) Dystocia was recorded for
2.82% of singleton births 1991-2002 (8.75% of cesareans).
Fetal distress: Fetal distress is a condition involving hypoxia (oxygen deprivation) and
metabolic acidosis (elevated blood level of lactic acid). The contractions of normal labor
result in a series of acute hypoxic events, which lead to some degree of acidosis;
however, severe oxygen deprivation (asphyxia) and acidosis can lead to neurologic
impairment or death. The fetal heart rate is monitored via intermittent examination with
a stethoscope or via continuous electronic monitoring. Certain fetal heart rate patterns are
believed to portend an adverse outcome, and the threshold for intervention is subject to
subjective clinical judgment. (12) Fetal distress is the second most commonly reported
indication for cesarean (14-20 % of cesarean deliveries) (35, 43) has a reported
67
sensitivity in the birth certificate data of less than 40%. Fetal distress was recorded for
3.67% of singleton births 1991-2002 (9.97 % of cesareans).
Prolonged labor (> 20 hours): There is a strong association between prolonged labor and
cesarean delivery. (153-155) Associations have been reported between prolonged labor
and maternal morbidity, specifically, prolonged first stage of labor (155) and infection
and between prolonged second stage, which is more often cited as an indication for
cesarean delivery, and postpartum hemorrhage, infection, and severe obstetric
lacerations. (154, 155) Prolonged labor was recorded among 0.86 % of singleton births
1991-2002 (1.47 % of cesareans).
Cephalopelvic disproportion: Cephalopelvic disproportion occurs when the either the
fetal head too large to pass through the maternal pelvis, because of the size of the fetal
head, the size of the maternal pelvis, or both. There is no reliable way using current
radiographic or ultrasound techniques to predict cephalopelvic disproportion, and the
diagnosis is often made following arrest of labor. (12) Cephalopelvic disproportion was
recorded among 2.27 % of singleton births 1991-2002 (10.33 % of cesareans).
Abruptio placenta: Abruptio placenta is separation of the placenta from the uterine
implantation site before delivery of the fetus. Some risk factors include diabetes,
hypertension, advanced maternal age, and alcohol or cigarette use during pregnancy.
Treatment entails IV fluids and blood transfusion, and emergency cesarean delivery may
be indicated. (152) Abruptio placenta was recorded among 0.54 % of singleton births
1991-2002 (1.50 % of cesareans).
Cord prolapse: Cord prolapse is a rare complication that occurs when the umbilical cord
drops through the cervix into the vagina ahead of the descending fetus. Due to the risk of
68
fetal oxygen deprivation, it is considered an emergency. Attempts must be made to
elevate the presenting part of the fetus in order to prevent cord compression. Immediate
delivery is required, typically via cesarean. Cord prolapse was recorded among 0.20 %
of singleton births 1991-2001 (0.61 % of cesareans).
Excessive bleeding: Excessive bleeding is responsible for the majority of maternal deaths
during childbirth in the United States. Excessive bleeding during labor is not clearly
defined, as most criteria for defining obstetric hemorrhage refer to postpartum, rather
than intrapartum bleeding. (156) Significant bleeding compromises both mother and fetus
and is often an indication for cesarean delivery. Causes of excessive bleeding during
labor may include placenta previa (placenta across the cervix), placenta accreta (abnormally
deep attachment of the placenta), abruptio placenta (premature detachment of the placenta
from the uterine wall), or uterine rupture. (156) A condition which may result excessive fetal,
rather than maternal, bleeding during labor is vasa previa, a condition in which fetal blood
vessels run in close proximity to the cervix. Rupture of the maternal membranes may result in
rapid exsanguination of the fetus. (156) Excessive bleeding was recorded for 0.55 % of
singleton births 1991-2002 (0.75 % of cesareans).
Placenta previa: Placenta previa is a complication of pregnancy in which the placenta
grows across the opening of the cervix, creating a risk of hemorrhage. Placenta previa
was recorded for 0.32 % of singleton births 1991-2002 (1.50 % of cesareans).
Premature rupture of membranes: Premature rupture of membranes (prior to
commencement of labor) occurs in approximately 8% of pregnancies. (12) Attempts are
made to induce labor by administering oxytocin, a hormone ordinarily produced by the
mother during labor. If this fails to induce sufficient contractions, cesarean delivery is
69
indicated. Premature rupture was recorded for 2.68 % of singleton births 1991-2002 (3.14 %
of cesareans).
Meconium staining: Meconium staining indicates that fetal bowel contents have passed
into the amniotic fluid. There has been a long-held belief that meconium is passed in
response to hypoxia, and its presence is a sign of fetal distress. More recent research
suggests that in some cases it is a normal physiological process. (12) Aspiration of
meconium can result in fetal lung damage.(12) Meconium staining was recorded for 5.65
% of singleton births 1991-2002 (percentage was also 5.65 for cesareans).
Table 3. Variables Considered for Inclusion the Fixed Effects Models*
Included Excluded Tort Variables
Caps on non-economic damages Collateral source offset Caps on contingency fees Periodic payments Modification of joint and several liability rule Patient compensation fund Statute of Limitations Statute of Repose Direct Tort Reforms Indirect Tort Reforms
Caps on or elimination of punitive damages awards Patient compensation funds
Birth Certificate Variables
Cesarean Birth Year State of Occurrence Maternal age Marital status Race Hispanic ethnicity Foreign-born mother Maternal education Parity Tobacco Diabetes Hypertension Adequacy of pre-natal care Breech or other malpresentation Gestational age Birthweight
Weekend birth Maternal Alcohol Use Incompetent cervix Eclampsia Previous preterm or small for gestational age infant Previous infant 4000 + grams Dystocia Fetal distress Prolonged labor (> 20 hours) Cephalopelvic disproportion Abruptio placenta Cord prolapse Excessive bleeding Placenta previa Premature rupture of membranes Meconium staining
* Table 4 contains several additional variables that were used in the descriptive analysis only.
70
Table 4. Variables Included in Descriptive and/or Econometric Analyses
Variables and Description NCHS Variable
Name
Category Classification
Caps on non-economic damages
N/A
Independent 1=Cap < 250,000 2=$250,000 < Cap < 500,000 3=$500,000 < Cap < 750,000 4=Cap > $750,000 (89) 0=absent 1=present
Collateral source offset
N/A Independent Continuous (fractions of a year in effect)
Contingency fees
N/A Independent Continuous (fractions of a year in effect)
Periodic payments
N/A Independent Continuous (fractions of a year in effect)
Modification of JSL N/A Independent Continuous (fractions of a year in effect)
Statute of Limitations N/A Independent Time limit in years Statute of Repose N/A Independent Time limit in years Direct Tort Reforms
N/A Independent 0=absent 1=present
Indirect Tort Reforms
N/A Independent 0=absent 1=present
Delivery Method
DELMETH5 UME_VAG UME_VBAC UME_PRIMC UME_REPEC
Dependent 1= vaginal (excludes VBAC) 2= VBAC 3= primary cesarean 4= repeat cesarean
Cesarean DELMETH5 UME_PRIMC UME_REPEC
Dependent 0=no 1=yes
Birth Year DATAYEAR DOB_YY
1991-2004
State of Occurrence STATENAT OSTATE
01-51
Day of week WEEKDAY DOB_WK
Confounder 1-7
Maternal age
DMAGE MAGER
Confounder 1= <20 2=20-24 3=25-29 4=30-34 5=35-39 6=40-45 7=45+
71
Table 4. Variables Included in Descriptive and/or Econometric Analyses
Variables and Description NCHS Variable
Name
Category Classification
Marital status DMAR MAR
Confounder 0=married 1=unmarried
Race MRACE MBRACE
Confounder 1= white 2 =black 3= Native American 4= Asian
Hispanic ethnicity ORMOTH UMHISP
Confounder 0=not Hispanic 1=Hispanic
Foreign-born mother MPLBIR UMBSTATE
Confounder 0=not foreign-born 1=foreign-born
Maternal education DMEDUC MEDUC6
Confounder 1= 0-8 years 2= 9-11 3= 12 (hs grad) 4= 13-15 y 5= 16 +
Parity DLIVORD LBO
Confounder 1=primiparous 0=multiparous
Tobacco TOBACCO TOBUSE
Confounder 0= does not smoke 1=smokes
Diabetes DIABETES URF_DIABETES
Confounder 0=absent 1=present
Hypertension CHYPER PHYPER URF_CHYPER URF_PHYPER
Confounder 0=absent 1=present
Adequacy of pre-natal care
PCV MONPRE NPREVIST MBCB PRECARE UPREVIS
Confounder 0=adequate, intermediate or intensive. 1=inadequate or no care
Breech presentation
BREECH ULD_BREECH
Confounder 0=absent 1=present
Gestational age
DGESTAT COMBGEST
Confounder < 32 wks (extremely premature) > 32 wks and < 36 (premature) > 37 wks and < 41 weeks (Term) > 41 wks (postmature)
Birthweight
DBIRWT DBWT
Confounder < 2500 g (LBW) > 2500 but < 4000 (NBW) > 4000 (high birthweight)
72
Table 5 lists numbers and percent missing for variables included in the fixed
effects analysis. For approximately 1% of births no delivery method was reported, and
for the tort reform variables, there were no missing variables. For most confounders, the
percent missing was less than 2%, however, the percentages were higher for receipt of
prenatal care (7.51%), maternal education (13.52%) and for smoking status (19.42%).
The percent missing data for race, age, and marital status of mother on birth certificates is
very small and values are imputed by NCHS. (31) Missing data for gestational age may
be more common for some subpopulations and for pre-term births. For computation of
gestational age, weeks of gestation were imputed for records with missing day of last
menstrual period when there is a valid month and year. (157) Missing information on
educational attainment varies by state, but, overall, according to the National Center for
Health Statistics, information was missing for just 2% of records in 2004. (157) The
educational attainment variables are not directly comparable across birth certificate
revisions. (31) Because maternal educational attainment is an important predictor of
cesarean delivery, it was included in the models. In re-coding, a decision was made to
lose, rather than misclassify observations. PROC GLM in SAS addresses missing values
via listwise deletion, deleting observations for which there is a missing value, which may
be a non-trivial number. Nevertheless, when the problem of missing data for a particular
variable does not depend on the dependent variable, listwise deletion produces generally
unbiased estimates and may be preferred over more complex statistical approaches, such
as maximum likelihood or imputation. (158)
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Table 5. Missing Values for Variables Included in Econometric
Analyses Variable
(Recoded from Originals)
Original Birth Certificate Variables
Variable Names % Missing or Coded
“Not Stated” Delivery Method Delivery
Method DELMETH5 UME_VAG UME_VBAC UME_PRIMC UME_REPEC
0.99
Race Race MRACE MBRACE
1.57
Hispanic Ethnicity
Hispanic Ethnicity
ORMOTH UMHISP
1.13
Age Age DMAGE MAGER
0.00
Education Education DMEDUC MEDUC6
13.52
Unmarried Marital status DMAR MAR
0.00
Foreign birth of mother
Foreign birth of mother
MPLBIR 0.12
Primipara/parity Live birth order
DLIVORD LBO
0.00
Diabetes Diabetes DIABETES URF_DIABETES
1.55
Hypertension Hypertension CHYPER PHYPER URF_CHYPER URF_PHYPER
1.55
Smoking Smoking TOBACCO TOBUSE
19.42
Inadequate Prenatal Care
Receipt of prenatal care
PCV MONPRE NPREVIST MBCB PRECARE UPREVIS
7.51
LBW, VLBW, HBW
Birthweight BW DBIRWT DBWT
0.10
Very Pre-term, Preterm, Postmature
Gestational age
DGESTAT COMBGEST
1.01
Breech Breech BREECH ULD_BREECH
0.04
74
Unmeasured confounders
There are several important confounders for which there are no data available
from the NCHS natality files.
Insurance status: Women who have private medical insurance are more likely to have a
cesarean delivery than those insured by a health maintenance organization or by public insurance
or without insurance. (21) (159) There is also a perception that patients with public
insurance (e.g., Medicaid) are more likely to bring suit, (160) This information is not
collected on the birth certificate. Yang et al. (107)adjusted for insurance status using
state-level data from the U.S. Census Bureau. Dubay et al. (105) used mother’s marital
status and educational attainment as proxies for both socioeconomic status and insurance
coverage. Yang et al. (107) used U.S. Census state-level data for each year on insurance
status (Medicaid, private, uninsured) among women to measure SES.
Socio-economic status: Studies have reported associations between cesarean delivery
and socioeconomic status that cannot be explained by maternal age, parity, birth weight,
race, ethnicity, or complications of pregnancy or childbirth. (161) Birth certificate data
provides no direct measure of socioeconomic status. Dubay al. (105) used mother’s
marital status and educational attainment as a proxies’ defensive responsive to
malpractice claims risk includes performing more cesarean deliveries on women in the
lower categories of socioeconomic status. Others have used educational attainment, Kim
using high school education or less than high school and Yang et all using college
education or less than college to represent socioeconomic status as a control variable in
their models. The present analysis will examine the effect of tort reform on cesarean
75
delivery, stratified by age, race, and educational status but not attempt to measure
socioeconomic status directly.
Maternal obesity: Maternal obesity is associated with several complications of
pregnancy, including macrosomia, gestational hypertension, preeclampsia, and
gestational diabetes. (135) and consequently with higher cesarean rates. Obesity among
the U.S. population, including women of childbearing age, has increased dramatically
over time. Although it is not possible to measure obesity, data are available for several
risk factors often associated with obesity, including hypertension and both pre-pregnancy
and gestational diabetes, which will be controlled for in the analysis. In order to control
for obesity in their study of tort reform and delivery method, Yang et al. (107) used data
on females (all ages) from the Behavioral Risk Factor Surveillance System (BRFSS) to
calculate state-level obesity rates.
Insurance carrier prohibition of VBAC: If insurance companies’ failure to cover VBAC
is a substantial contributor to cesarean rates, this will confound the association between
tort reform and physician decision to perform a cesarean. This could be controlled by
limiting the analysis to primary cesarean deliveries; however, it is not possible to reliably
distinguish between primary and repeat cesareans using birth certificate data.
Tort Reform Analysis
Panel data consists of “repeated measures” on an individual. Although this study
used individual-level data for 54 million singleton births, the unit of observation was the
state, rather than the individual birth, as tort reforms operate at the state level. For each
state, cesarean delivery (yes/no) was measured for each of the 14 years under study.
76
Fixed Effects Modeling
An “effect” (each term in a statistical model) is either “random” or “fixed.” A
fixed effect is an effect that is assumed to be constant for each unit of observation (in this
case a state) for each measurement (in this case each of 14 years), while a random effect
is one that is not fixed. Models in which all effects are fixed are called “fixed-effects”
models, and those in which all the effects are random are called “random-effects”
models. A hybrid, containing both, is called a “mixed-effects” model.
There is considerable state-to-state variability in cesarean rates. For each state, the
cesarean rate is likely affected by a set of factors, some measureable and some not,
unique to that state. Thus, changed in cesarean rates within states over time was
measured. Fixed effects modeling was used to reduce “unobserved variable bias,” a term
used in economics to describe the effect of unknown confounders, at the state and year
level. This controls for omitted but fixed variables at the state level, those that either are
unidentified or cannot be measured. In the absence of tort law change, cesarean rates are
determined by the sum of a state effect that is stable over time and a year effect that is
common across states.
“Differences in differences” is fixed effects methodology for aggregated data that
is similar to a pre-test, post-test experiment. It is often specifically used to estimate the
impact of state-level policy change. “Other things equal” (ceteris paribus) is an
assumption that everything, apart from the variables of interest and variables for which
control can be achieved, remains the same. Therefore, the unobserved differences
between the two groups are the same over time. It is also assumed that, were it not for the
implementation of tort reforms, the general trend in rates would be the same for the group
77
of states that has implemented reforms and that which has not. In this case, states that did
not implement reforms act essentially as a control group for those that did implement
reforms. The present analysis compares probability of cesarean delivery before and after
tort reform for states that implemented tort reform (essentially the “treatment” group)
with changes in occurrence for states that did not implement tort reforms (“control”
group). This approach accounts for differences in outcomes between the states that
existed before implementation of the tort reforms. Other things equal, in states that that
have adopted certain tort reform measures, the probability of having a cesarean delivery
is lower following implementation of the reform measures.
In an ecologic analysis, it is not possible to be sure that any observed changes in
occurrence of cesarean delivery were due to changes in tort law. It is, however, possible to be
sure that the changes were due to some factor that changed over time within each state and that
changes in cesarean delivery were not due to characteristics within the states that were fixed over
time, because the fixed effects analysis controls for these characteristics. What is often cited as a
limitation of fixed effects methodology is an increase in sampling variability. (162) Of course,
that limitation does not apply to this study, which utilizes a 100% sample.
Omitted Variable Bias and Endogeneity
“Omitted variable bias” is bias in a parameter estimate in a regression analysis
that occurs when a variable that should be in the model has been omitted. Despite the use
of fixed effects modeling to reduce the likelihood of omitted variable bias, there were
several possible confounders that could not be measured using birth certificate data.
Individual-level variables that could not be measured included insurance status, socio-
economic status, and maternal obesity. Additionally, within-state local area patterns of
78
medical practice and insurance company practices, such as prohibition of VBAC, that
may influence cesarean delivery, could not be measured.
An “endogenous” variable is one whose value is determined by other variables in
the model, as opposed to an “exogenous variable,” the value of which is unrelated to the
variables in the model. Endogeneity was of concern in this analysis, because tort reforms
in some states may have been enacted in response to a perceived malpractice crisis,
characterized by increases in malpractice insurance premiums, malpractice lawsuits, and
and/or damage awards. In some states, tort reform has been limited to medical
malpractice cases in response to a perceived crisis specifically in medical malpractice
cases. Obstetrics is the most common specialty involved in malpractice suits, and
negligent failure to perform a cesarean is a common cause of action in those lawsuits.
Cesarean rates may therefore, in some cases, have an influence on enactment of some tort
reforms. Endogeneity could result in an underestimate of the effect of tort reforms if
reforms were adopted in response to increasing cesarean delivery rates. If both adoption
of tort reforms and increasing cesarean rates are associated with an omitted variable, an
overestimate of the effect could result.
Data analysis was performed using SAS (SAS, Inc., Cary, NC). The SAS
procedure employed will be PROC GLM, with dummy variables for each year and for
each state. PROC GLM (generalized linear models) is a procedure used to perform
analysis of variance for repeated measures and is particularly useful for fixed effects
modeling that uses a large number of dummy variables. Adding the “solution” option in
PROC GLM produces a table of parameter estimates.
79
Ordinarily PROC GLM would not be used with a dichotomous outcome variable,
as it uses ordinary least squares regression, which, when used with a categorical variable,
may cause an “incidental parameters problem.” This occurs in repeated measures when
the number of observations increases with the number of measurements, and results in
parameter estimates that are biased upwards. (162) The annual number of births remained
relatively constant across the 14-year study period (Table 6), with a mean of 3,873,208 ,
and all 50 states were observed for each of the 14 years. For this reason, incidental
parameters should not be a problem. Some texts recommend use of the PROC PHREG
procedure, ordinarily used for survival analysis, for fixed effects analysis with a
dichotomous outcome; however, the procedure is not appropriate for use with the large
number of dummy variables needed for this analysis. (163)
Table 6. Numbers of Live Singleton Births Per Year, United States, 1991-2004
Year Number 1991 4,115,342 1992 4,069,428 1993 4,004,523 1994 3,956,925 1995 3,903,012 1996 3,894,874 1997 3,884,329 1998 3,945,192 1999 3,963,465 2000 4,063,823 2001 4,031,531 2002 4,027,376 2003 4,096,092 2004 4,118,907
Confounders that were known, could be measured, and for which data are
available, were included as variables in the models. Confounders that were unknown or
not measurable, “unobserved” but fixed confounders, were accounted for via fixed the
effects modeling.
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CHAPTER 4
RESULTS Descriptive Analyses
Between 1991 and 2004, there were 54,445,327 (approximately 3, 900,000 per
year) live singleton births in the United States, 74.9% delivered vaginally, and 21.8%
delivered via cesarean. (Table 7) The rate of cesarean delivery varied by state from 16.0
per 100 live singleton births (16.0%) in Alaska to 27.3 in Louisiana. (Table 8)
Changes in tort law between 1991 and 1994 by state are summarized in Table 9.
Non-economic damages caps were in effect in 29 states over the 14-year study period,
and eight states underwent changes in caps, either adopting, removing, or changing the
cap amount. Removal of a cap may result from either legislative or judicial actions, such
as invalidating a cap under a state’s constitution. Laws requiring disclosure of collateral
sources were in effect in 30 states, with 3 making changes in their laws during the study
period. The number of states with joint and several liability reforms in place increased
from 25 to 30 over the study period. Periodic payment requirements were in effect in 33
states. All states had statutes of limitations in effect throughout the 14-year period, which
varied in length by state. Statutes of limitations ranged from 1 year to 4 years, with a
mean of 2.2 years. Statutes of repose had been adopted by 38 states, and they were
present for all 14 years in 37 of those states. Among states with statues of repose, the
length ranged from 2 to 10 years, with a mean of 4 years. Throughout the study period,
the same thirteen states had limits on attorneys’ fees in place.
Rates of cesarean and vaginal delivery according to maternal demographic
characteristics and medical history are presented in Table 10. The highest rate of cesarean
81
birth was among black women compared to other racial and ethnic groups. Over the 14-
year period, the percentage of cesareans per 100 live singleton births increased with
maternal age. Among mothers aged 45 and older, 37.9% of births were delivered via
cesarean, while among women aged less than 20 years, 18.0% of births were delivered
via cesarean. Nearly 40% of women diagnosed with either chronic or gestational diabetes
and or women with either chronic or pregnancy-associated hypertension underwent
cesarean delivery. Further, 85% of breech or other malpresentations were delivered via
cesarean.
Among gestational age categories (11), the highest rate of cesarean delivery
(38.9%) was among “very premature” infants, those aged 32 weeks or less. The highest
rate of cesarean delivery by birthweight (32.7%) was in the premature category (<36
weeks). Figure 3 shows the trend in cesarean rates among live singleton births from 1991
through 2004. The rates are lower than those typically reported nationally, because
multiple births have been excluded.
Table 7. Live Singleton Births by Delivery Method, United States, 1991-2004
Number Percentage of
Live Singleton Births
Total Annual Mean Live Singleton births 54,224,912 3,873,208 100.0 Delivery Method Vaginal 40,621,058 2,901,504 74.9 VBAC 1,251,784 89,413 2.3 Primary Cesarean 7,188,648 513,475 13.3 Repeat Cesarean 4,631,839 330,846 8.5 All Cesarean 11,820,487 844,321 21.8 Not reported 531,583 37,970 1.0
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Table 8. Cesarean Deliveries (Live Singleton Births) by State,
Ordered by Rate, United States, 1991-2004
State Mean Cesarean Births per Year
Rate Per 100 Live Singleton Births
Louisiana 17,831.0 27.3 Mississippi 10,831.6 26.9 Arizona 8,916.6 25.9 West Virginia 5,383.5 25.1 New Jersey 27,336.5 25.1 Alabama 14,383.5 24.6 Texas 81,979.9 24.1 Florida 46,031.4 23.8 South Carolina 12,043.4 23.7 Tennessee 18,333.1 23.3 Kentucky 11,910.6 23.3 New York 59,761.1 23.2 Delaware 25,18.6 23.0 Virginia 20,647.1 22.5 North Carolina 24,061.2 22.4 California 118,339.5 22.1 Georgia 26,273.6 22.0 Maryland 14,662.2 21.9 Massachusetts 17,414.2 21.8 Missouri 16,302.4 21.7 Maine 2,900.3 21.3 Nevada 5,682.6 21.2 South Dakota 2,230.5 21.2 Nebraska 4,971.7 21.1 Kansas 7,665.8 21.0 Indiana 17,339.2 21.0 Rhode Island 2,671.0 20.9 Michigan 2,7219.5 20.9 Oklahoma 9,543.0 20.7 Ohio 30,608.6 20.4 Illinois 35,810.4 20.3 Iowa 7,262.9 19.7 Connecticut 8,418.4 19.6 New Hampshire 2,728.9 19.6 Montana 2,080.1 19.3 North Dakota 1,738.7 19.0 Washington 14,367.2 18.8 Pennsylvania 30,690.5 18.8 Oregon 8,287.6 18.5 Wyoming 1,095.2 18.5 Arkansas 13,568.7 17.7 Vermont 1,118.2 17.5 Minnesota 11,177.8 17.4
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Hawaii 3,103.6 17.3 New Mexico 4,482.4 16.9 Colorado 9,874.4 16.8 Idaho 3,079.0 16.7 Wisconsin 11,011.9 16.7 Utah 7,046.3 16.2 Alaska 1,602.9 16.0
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Table 9. Number of States with Tort Reforms in Effect by Year, 1991-2004
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Non-economic damages caps
25 23 23 23 25 25 26 25 25 23 23 24 27 27
Cap < $250,000 * 3 3 3 3 4 4 4 3 3 3 2 2 2 8 Cap > $250,000 and < $500,000*
9 8 9 8 9 10 10 12 12 12 13 13 14 15
Cap > $500,000 and < $750,000 *
8 8 7 8 8 8 10 8 8 6 6 6 9 3
Cap > $750,000* 4 4 4 4 3 3 2 2 2 2 2 2 1 1 Collateral Source 30 30 29 29 29 29 29 29 29 29 28 29 30 30 Joint and Several Liability
25 26 26 26 29 30 30 29 29 29 29 31 33 33
Periodic Payments 27 27 27 27 26 27 27 27 27 27 27 29 30 30 Statute of Limitations 50 50 50 50 50 50 50 50 50 50 50 50 50 50 Statute of Repose 37 37 37 37 37 37 37 38 38 38 37 38 38 39 Limit on Attorney Fees 13 13 13 13 13 13 13 13 13 13 13 13 13
*Amounts represent caps in year 2004 dollars, rather than the nominal statutory cap amounts.
85
Table 10. Maternal Characteristics by Delivery Method, Live Singleton Births, United States, 1991-2004 Characteristics Cesarean Births
Percent Maternal Race White 21.6 Black 22.7 Native American 18.9 Asian 20.8 Hispanic Ethnicity 21.5 Foreign-born mother 21.4 Maternal Age < 20 18.0 20-24 18.9 25-29 21.6 30-34 24.6 35-39 28.7 40-44 33.0 45+ 37.9 Maternal Education 0-8 years 18.4 9-11 years 18.5 12 years 21.9 13-15 years 23.2 16+ years 24.9 Marital Status: Single 20.0 Primipara 23.5 Smoking 21.3 Diabetes 36.7 Hypertension 37.4 Adequacy of Prenatal Care* Intensive 27.8 Adequate 23.8 Intermediate 20.0 Inadequate 17.2 No care 14,8 Missing/unknown 22.6 Breech or other malpresentation
85.2
*Based on revised graduated index algorithm (R-GINDEX, Alexander, Kotelchuck 1996) (142)
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Table 11. Infant Characteristics by Delivery Method, Live Singleton Births, United States, 1991-2004
Characteristics Cesarean Births
Percent Vaginal Births
Percent Gestational Age < 32 wks 38.9 60.3 32-36 weeks 27.9 71.20 37-41 weeks 21.3 77.8 41+ weeks 21.47 77.6 Birthweight < 2500 g 32.7 66.4 2500- 4,000 20.1 78.9 >4,000 29.4 69.5 1 > 1 and < 499 13.5 85.5 2 >500 and < 1499 51.2 47.9 3 >1500 and < 2499 29.5 69.6 4 >2500< and < 4249 6.7 78.6 5 > 4250 and < 8165 6.8 65.3
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Table 12. Cesarean Deliveries (Live Singleton Births) by State, 1991 and 2004 1991 2004 Percent Increase Alabama 24.4 30.0 18.6 Alaska 15.4 19.6 21.1 Arizona 17.5 22.1 28.5 Arkansas 26.7 29.5 26.8 California 21.5 27.8 21.5 Colorado 15.6 22.5 27.4 Connecticut 20.6 28.4 27.9 Delaware 21.6 28.9 30.8 Florida 23.1 31.8 26.8 Georgia 21.4 27.8 21.8 Hawaii 19.8 22.8 19.6 Idaho 17.2 20.6 24.9 Illinois 21.3 25.9 24.6 Indiana 20.8 25.6 23.6 Iowa 19.8 24.6 25.9 Kansas 22.5 26.9 29.9 Kentucky 24.1 30.9 30.0 Louisiana 27.3 31.0 25.2 Maine 20.6 26.2 27.4 Maryland 22.7 28.4 28.0 Massachusetts 21.3 29.0 25.3 Michigan 20.7 26.3 21.9 Minnesota 16.3 22.9 30.4 Mississippi 25.8 31.4 26.6 Missouri 21.6 27.6 23.2 Montana 19.1 24.2 26.6 Nebraska 18.8 27.6 27.1 Nevada 19.5 28.1 23.4 New Hampshire 20.0 24.4 31.7 New Jersey 23.0 32.7 18.6 New Mexico 17.9 19.6 27.9 New York 22.6 28.9 26.0 North Carolina 21.7 27.0 22.2 North Dakota 18.3 23.2 24.4 Ohio 22.6 25.4 28.9 Oklahoma 19.8 29.9 24.6 Oregon 18.1 25.6 25.3 Pennsylvania 21.4 26.3 26.3 Rhode Island 18.7 27.3 29.0 South Carolina 21.6 30.0 23.7 South Dakota 19.6 24.7 28.1 Tennessee 22.6 29.1 28.9 Texas 26.3 29.9 18.2 Utah 16.9 19.2 21.8 Vermont 18.8 22.8 27.9 Virginia 22.2 28.9 25.1 Washington 18.4 26.1 30.9
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Table 12. Cesarean Deliveries (Live Singleton Births) by State, 1991 and 2004 1991 2004 Percent Increase West Virginia 25.2 31.9 20.4 Wisconsin 16.7 21.4 21.6 Wyoming 18.6 22.6 18.6
21.8 21.4 20.9 20.3 19.9 19.7 19.7 20.0 20.8 21.723.2
24.726.1
27.6
0
5
10
15
20
25
30
35
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2001 2003 2004
Perc
ent
Figure 2. Percent of Cesarean Deliveries Among Live Singleton Births, United State, 1991-2004
18.7 (27.3)
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Fixed Effects Analysis
The final models are presented in Table 13, the first model including tort reforms
categorized as direct and indirect, and the second model defining damages caps as a
dichotomous yes/no variable. In alternate specifications, caps were modeled in four
levels, as a continuous variable, as an indicator variable including fractions of a year in
effect, and a version with all tort reform variables coded as dichotomous. Results of these
alternate specifications are presented in Table 14. Parameter estimates differed for each
model, but in all cases the effect of tort reforms on cesarean delivery was minimal.
Coefficients ranged from -.01-0.03 for individual tort reforms. Results varied
somewhat with model specifications defining non-economic damages caps in different
ways, but the difference was small. The effect of direct reforms on cesarean rates,
adjusting for maternal demographic characteristics, maternal medical conditions, and
characteristics of labor and delivery, was greater than was the effect for indirect tort 1
reforms. However, the difference was small, -0.009 compared to -0.004. Non-economic
damages caps were associated with a 0.2% reduction in cesarean deliveries, with a
slightly greater effect shown for collateral source laws (2.0%) and statutes of limitations
(1.7%). Several reforms were associated with slight increases in cesarean delivery, joint
and several liability reform (0.1%), statutes of repose (0.1%), and limits on attorneys’
fees (0.6%).
Table 15 presents the results of the subset analysis by race and Hispanic ethnicity.
There was a small reduction in cesarean deliveries among white and Native American
mothers and a slight increase among black mothers. Collateral source rule modifications,
periodic payments, and statute of limitations changes showed a reduction in cesarean
90
deliveries for all groups. Limits on attorneys’ fees showed an increase in cesarean
delivery for all groups, with a greater effect for Native American and Asian than for
white and black mothers. For five of the seven tort reforms, the effect on cesarean
delivery was greater for Native American mothers than for mothers of other racial
groups.
Table 16 presents the results of the subset analysis for maternal educational
attainment and marital status. Damages caps showed a greater reduction in cesarean
deliveries among mothers with 13-15 years of education than other educational
categories. Among unmarried mothers, the effect of non-economic damages caps was a
1.3% increase in cesarean deliveries and for collateral source rule, a 0.3% increase. Each
of the other reforms was associated with a small decrease in cesarean deliveries for
unmarried mothers.
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Table 13. Parameter Estimates* for the Effect of Direct and Indirect Tort Reforms on Cesarean Delivery
Reforms Categorized as Direct or
Indirect
Individual Reforms
Direct Tort Reforms -0.009 - Non-Economic Damages Cap (Yes/No)
- -0.002
Collateral Source - -0.010
Indirect Tort Reforms -0.004 - Joint and Several Liability - 0.001 Periodic Payments - -0.007 Statute of Limitations - -0.017 Statute of Repose - 0.001 Limit on Attorney Fees - 0.006 Confounders Race -0.002 -0.002 Hispanic ethnicity -0.001 < -0.001 Maternal age 0.032 0.032 Educational attainment 0.003 0.003 Unmarried mother -0.008 -0.007 Foreign birth of mother -0.005 -0.006 Primipara 0.047 0.047 Diabetes (chronic or gestational) -0.038
-0.038
Hypertension 0.026 0.026 Smoking 0.001 -0.002 Inadequate prenatal care -0.031 -0.030 Very preterm birth 0.081 0.081 Preterm birth 0.027 0.026 Postmature birth 0.008 0.008 Low birthweight 0.082 0.082 High birthweight 0.128 0.128 Breech or other malpresentation 0.042
0.043
* All significant at p <.0001 except for Hispanic (significant at .006).
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Table 14. Alternative Model Specifications 1 2 3 4 5 6 Cap Modeled in
Four Levels Cap as
Continuous Variable
Cap Indicator 1 (including
fractions of a year in effect)
Includes Cap Indicator 1 and Continuous Cap Variable
Cap indicator 2 (yes/no), Each Other Reform
as Fraction of a Year
Cap Indicator 2 (yes/no), Each Other Reform
Yes/No
Cap indicator 1 - - -0.005 0.016 - - Cap indicator 2 - - - - -0.002 0.011 Adjusted cap (continuous) - < -0.001 - -0.004 - - Cap < $250,000 0.033 - - - - - Cap > $250,000 and < $500,000 -0.002 - - - - - Cap > $500,000 and < $750,000 -0.020 - - - - - Cap > $750,000 -0.031 - - - - - Collateral Source -0.011 -0.012 -0.011 -0.013 -0.010 -0.009 Joint and Several Liability 0.001 -0.002 < 0.001 -0.001 0.001 0.013 Periodic Payments -0.012 -0.006 -0.006 -0.012 -0.007 ** Statute of Limitations -0.015 -0.019 -0.018 -0.017 -0.017 ** Statute of Repose 0.002 0.003 0.002 0.003 0.001 0.003 Limit on Attorney Fees 0.006 0.007 0.006 0.008 0.006 -0.007 * All significant at p < .0001 except those reported as not uniquely estimable. ** Reported by SAS as not uniquely estimable.
93
Table 15. Parameter Estimates,* Effect of Tort Reforms on Cesarean Delivery by Race White Black Native
American Asian Hispanic
Ethnicity Cap (yes/no) -0.004 0.002 -0.009 <0.001 0.012 Collateral Source -0.009 -0.011 -0.007 -0.004 -0.030 Joint and Several Liablity 0.001 0.012 -0.025 0.004 0.052 Periodic Payments -0.007 -0.002 -0.035 -0.008 0.018 Statute of Limitations -0.017 -0.008 -0.016 -0.021 0.013 Statute of Repose 0.002 <.0001 0.003 0.002 -0.002 Limit on Attorney Fees 0.005 0.003 0.029 0.014 **
* Controlling for race (in ethnicity model), Hispanic ethnicity (in race model), maternal age, educational attainment, unmarried mother, foreign birth of mother, primiparas, diabetes (chronic or gestational) hypertension (chronic or gestational), smoking status, inadequate prenatal care, very preterm birth, preterm birth, postmature birth, low birthweight, high birthweight, and breech or other malpresentation.
Table 16. Regression Coefficients, Effect of Tort Reforms on Cesarean Delivery by Maternal Educational Attainment and Marital Status Educational Attainment Marital
Status
< 8 years 9-11 years
12 years
13-15 Years
15+ years
Unmarried
Cap (yes/no) -0.001 ** -0.001 -0.006 -0.012 -0.004 0.128 Collateral Source -0.016 -0.012 -0.011 -0.010 -0.009 0.031 Joint and Several Liablity 0.009 0.005 0.001 -0.004 0.003 -0.007 Periodic Payments -0.003 -0.003 -0.005 -0.005 -0.008 -0.010 Statute of Limitations -0.013 -0.015 -0.017 -0.019 -0.017 -0.024 Statute of Repose 0.002 0.001 0.001 0.002 0.003 -0.037 Limit on Attorney Fees 0.007 0.004 0.005 0.006 0.004 -0.008
* Controlling for race, Hispanic ethnicity, maternal age, educational attainment (in marital status model), unmarried mother (in educational attainment model), foreign birth of mother, primiparas, diabetes (chronic or gestational) hypertension (chronic or gestational), smoking status, inadequate pren atal care, very preterm birth, preterm birth, postmature birth, low birthweight, high birthweight, and breech or other malpresentation. **p> .05
94
CHAPTER 5
CONCLUSIONS
Based on this analysis, the effect of tort reforms on cesarean delivery and on
defensive medicine appears to be minimal. This finding does add support to other
literature reporting little or no effect of tort reforms on defensive medicine which has
important implications for both tort reform and maternal and child health.
The testable hypothesis for this analysis was “Other things equal, in states that have
adopted certain tort reform measures, the probability of having a cesarean delivery is
lower following implementation of the reforms,” or, framed as a null hypothesis, “Other
things equal, in states that that have adopted certain tort reform measures, implementation
of the reforms had no effect on cesarean delivery rates.” Given the extremely small effect
found in this analysis, it is not reasonable to reject the null hypothesis of no effect.
Two research questions, one with four hypotheses and one with a single hypothesis,
were to be evaluated by this study (page 45), each proposing that tort reforms would
decrease the probability of cesarean delivery.The five hypotheses are not supported by
the results of the analyses. The hypotheses that tort reforms, particularly non-economic
damages caps, would reduce cesarean delivery rates were based on the findings of other
researchers, as discussed in Chapter 2. (102, 105, 107), (111),
The findings of the present study could mean that defensive medicine does not
exist, that defensive medicine is not a large component of the increase in cesarean rates,
or that physicians do not respond to tort reforms by modifying clinical practice. There are
also several other possible explanations for the findings.
95
Although the dataset included 54 million live singleton births, small numbers may
have been a problem due to the small number of changes in tort laws during the study
period. Particularly when dividing non-economic damages caps into levels, numbers for
each year were very small. For example, caps of $250,000 or less, the level hypothesized
to have the greatest effect on cesarean delivery, were in effect for a mean number of 3.4
states per year. It may be that the number of data points was simply insufficient to show
the anticipated effect.
It is also possible that there are unobserved time varying factors exerting a greater
influence than the effect of state-level tort reform on the decision to perform a cesarean
delivery. Examples of factors that might have an effect of this type within a particular
state are changes in physician practice patterns over time, changing political factors, and
insurance-related changes affecting either malpractice insurance or patient procedure use.
A change sufficient to obscure a relationship between tort reforms and cesarean is likely
on a broader scale than one or two states. Further, the data were examined for extreme
outliers to explore whether perhaps a few states with both very high caps and high
cesarean rates could be driving parameter estimates, but no such outliers were found.
This study addresses non-economic damages but not economic damages. Caps on
non-economic damages would not reduce liability if economic damages are high, and
legal cases involving catastrophic birth injuries, for example, are of very high value.
Economic damages, which may include lifetime wage loss and custodial care, may be
valued in the millions of dollars. Additionally, it has been reported that the presence of
non-economic damages caps may increase economic damages awards. (164)
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Strengths
The two databases used in the study are among its strengths. The birth certificate
data includes all recorded births in the United States 1991-2004. Some variables on the
birth certificate are more reliable than others; however, for the outcome variable,
cesarean delivery, sensitivity is reportedly greater than 98%. Data for the maternal
characteristics and birth characteristics most likely to confound an association between
tort reform and cesarean delivery were adequately captured by the data, and it was
possible to control for them. The tort reform database used for the study was
meticulously researched and validated, (111) whereas some prior studies have relied upon
compilations containing omissions and miscoding (109)
Use of fixed effects methodology is a strength of the study, as it controlled for
potential unobserved confounding factors within states that were fixed over the 14-year
study period and factors that varied among states.
Limitations
This study overcomes limitations of some earlier studies, which include use of
data from only one or a few states or a few years, aggregation of birth data to the state or
county level, rather than use of individual level data for birth certificate variables, and use
of incomplete tort reform information. This study does, however, have several
limitations.
Among the study’s limitations are those inherent in analysis of secondary data.
Use of secondary data limits the variables available for analysis to those included in the
dataset, rather than those that might be ideal for addressing a particular research question.
97
(51) Use of data collected, coded, and re-coded by others is challenging, and the
investigator must develop an understanding of variable definitions, variable coding, and
the reliability of individual data elements in order to analyze and interpret the data. (51)
Limitations specific to use of birth certificate data include variation in reliability
and validity of data elements. Many of the birth certificate variables, particularly labor
and delivery characteristics, are significantly underreported in the birth certificate data,
some with sensitivity rates of less than 20%. This low level of sensitivity may represent
differential reporting by maternal demographic characteristics or according the birth
characteristics, with more complete reporting for adverse outcomes, as the complications
are checked off on the certificate after the outcome is already known. This makes many
variables, many of which have been included in the analyses of other researchers,
inappropriate for inclusion in the models. The final list of confounders for inclusion in
the models in this study was comprised of only those considered most important and most
reliably captured in the data: maternal age, race, Hispanic ethnicity, foreign birth,
education, marital status, parity, diabetes, hypertension, tobacco use, pre-natal care
utilization and the fetal characteristics of gestational age, birthweight, and non-vertex
presentation. Additional analyses characterized seven tort reforms by state and year.
There is a possibility of residual confounding as a result of factors that varied over
time and were either unobserved or could not be adequately measured. Several important
confounders for which no data were available are maternal insurance status, maternal
socioeconomic status, prevalence of maternal obesity, and insurance carrier policies on
VBAC. Failure to adjust for these confounders may have somewhat attenuated an effect
of tort reforms on cesarean delivery but are unlikely to have been solely responsible for
98
the lack of effect. Two important potential confounders were too unreliably reported in
the birth certificate data for inclusion in the models, dysfunctional labor and fetal distress.
According to obstetric texts, (12) the majority of cesarean deliveries are performed for
one of these two indications, yet in the descriptive analysis, among live singleton births
delivered via cesarean, just 8.75% of the birth certificates reported dysfunctional labor as
a complication and 9.97% reported fetal distress.
Endogeneity was of concern in this analysis, because tort reforms in some states
may have been enacted in response to a perceived malpractice crisis, characterized by
increases in malpractice insurance premiums, malpractice lawsuits, and and/or damage
awards. In some states, tort reform has been limited to medical malpractice cases in
response to a perceived crisis specifically in medical malpractice cases. Obstetrics is the
most common specialty involved in malpractice suits, and negligent failure to perform a
cesarean is a common cause of action in those lawsuits. Cesarean rates may therefore in
some cases have an influence on enactment of some tort reforms. Endogeneity could
result in an underestimate of the effect of tort reforms if reforms were adopted in
response to increasing cesarean delivery rates. If both adoption of tort reforms and
increasing cesarean rates are associated with an omitted variable, an overestimate of the
effect could result.
Fixed effects specifications will not control for time-varying state-level
characteristics. If provider density, legal climate, political climate, obstetric practice
patterns, or any of a variety of and social and economic factors changed within states
over the study period, it is possible that these factors affected the results.
99
Although limiting the study to live singleton births prevents over-counting of
cesarean deliveries, it limits generalizability to all births. Multiple gestation pregnancies
are at high risk for low birthweight and preterm birth. (51) Although multiple births
represent just 1.7% of all births, 65.5% of multiple gestation pregnancies are delivered
via cesarean, (165) and rates of multiple birth have increased over time. (20)
Implications
There has been great concern since cesarean rates resumed their rise in the late
1990’s, following a brief decline, that the rates are too high, and the pattern of increase
has continued each year. How high is too high? There is no clear standard, and likely
different standards should apply to different groups of pregnant women. Rates of both
maternal and infant mortality have decreased dramatically since cesarean delivery
became readily available early in the last century. Nevertheless, it appears that in many
cases, cesarean is performed based on some small risk of an adverse outcome or perhaps
related to some element of personal choice on the part of the mother or physician. This
exposes mother and fetus to surgical risk and deprives them of benefits associated with
natural vaginal birth. The role defensive medicine may play in the decision to perform
surgery is not fully understood.
The question of whether tort reforms have the potential to curtail increases in
cesarean rates has not been answered. One explanation for the results observed in this
study is that there is truly no effect of tort reform on cesarean delivery. If this is true,
other approaches to addressing the desired reduction in cesarean rates should be pursued.
Increasing the number of women offered a trial of labor, with a consequent increase in
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VBAC rates, which will likely occur as a result of ACOG’s August 2010 revised VBAC
recommendations, (166) is one such approach. The incidence of maternal choice cesarean
has not been well-established. Some reports assert that women seek cesarean delivery for
reasons of convenience, (167, 168) while others counter that elective cesareans without
clear medical indication are more likely performed because of physician convenience.
(168) Elective induction of labor for reasons of convenience has also been reportedly
increasing. (169) Induction of labor has been found to be associated with cesarean
delivery, particularly for a first birth, (170) as the induction agent may fail to induce
contractions sufficient for a vaginal birth. Induction of labor in post-dates pregnancies
has become routine. (171) Reducing cesarean deliveries in each of the foregoing
circumstances, in the absence of clear medical indications, would contribute to curbing
the cesarean rate. Lowering the rate of cesarean delivery in the absence of clear medical
indications would, in turn reduce morbidity due to iatrogenic prematurity. Late pre-term
delivery (37-38 weeks gestation) has been increasing and is associated with significant
morbidity. (172)
This study has several implications for maternal and child health. Firstly, it should
be noted that the small percentage by which cesarean deliveries were reduced represents
large numbers of births. Among approximately 4 million live births in the United States
in 2009, 32.9% were cesarean deliveries. (2) Secondly, if tort reforms do not contribute to
reduction in cesarean rates, attention must be focused on other means of achieving
reduction goals specified by Healthy People 2020. (26) These other means include
avoiding cesarean delivery in the absence of clear medical indications, reducing induction
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and stimulation of labor, which can lead to cesarean delivery, and increasing trials of
labor leading to VBAC.
There are several implications for tort reform. Adoption of some reforms (non-
economic damages caps, collateral source rule modifications, and shorter statutes of
limitations) may result in a small reduction in defensive medicine but are not
alone are likely insufficient to significantly reduce defensive medicine. Damages caps
and modifications to the collateral source rule have also been shown to be associated with
other measures of malpractice pressure (i.e., malpractice insurance premiums), and the
findings of this study support their adoption as part of a strategy for reducing defensive
medicine. This study supports findings of other studies that other reforms are less likely
to reduce defensive medicine.
In this study, cesarean delivery is used as a marker for defensive medicine. This
study found only a small effect of tort reforms on cesarean delivery. A stronger finding
would have provided greater empirical support for the existence of defensive medicine.
There is, nonetheless, strong anecdotal evidence that defensive medicine is widely
practiced, which is supported by a number of physician surveys. Lack of effect of tort
reform on cesarean delivery could mean that defensive medicine does not exist but more
likely means that physicians do not respond to tort reform by modifying clinical practice.
Carrier et al. conducted a survey of a nationwide sample of physicians, reporting that
physicians indicated a level of concern over the possibility of being sued that is
disproportionate to their actual risk and that concern appears relatively insensitive to tort
reform. (81) The idea that damages caps would reduce defensive medicine assumes that
the greatest motivation for defensive medicine is fear of large jury verdicts. It may be that
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physicians’ real concern in avoiding lawsuits is more focused on non-economic aspects
of a lawsuit, such as reputational harm and the unpleasantness associated with lawsuits.
Empirical evidence demonstrating the existence of defensive medicine and whether it is
reduced by tort reform is still very much needed and calls for further research.
As stated in one of the introductory paragraphs of this document, “defensive
medicine is a complex phenomenon”. The findings of this study do not show that the
practice of defensive medicine does not exist but rather confirmed that it is difficult to
measure. Whether tort reforms can curtail defensive medicine or increasing cesarean rates
has not been resolved, but this study lends support to other reports that the likely effect is
small. Other factors, alone or in combination with defensive medicine practices, are yet to
be identified or fully explored to stem the rise and reduce the overall rate of cesarean
section births in the U.S.
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APPENDIX A
INSTITUTIONAL REVIEW BOARD APPROVAL FORM
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