Preconception and prenatal care

Preconception and prenatal care

Joshua H. Barash, MD*, Lara Carson Weinstein, MDDepartment of Family Medicine, Thomas Jefferson University,

833 Chestnut Street, Suite 301 Philadelphia, PA 19107, USA

In an era of changing and challenging paradigms, prenatal care has beencalled to task to answer for its purported effectiveness in improving maternaland infant health. Recent critical reviews have challenged the notion thatprenatal care as practiced in the United States improves birth outcomes[1,2,3]. In light of these recent challenges, this chapter will review the currentcontroversies that exist regarding the effectiveness of prenatal care as pre-ventive medicine. Then, on a more practical level, individual componentsof prenatal care will be critiqued using an evidence-based approach.

‘‘Prenatal care’’ is a heterogeneous concept involving a combination ofambulatory visits to health professionals, laboratory screening, and diag-nostic imaging. Adding to the complexity is the fact that prenatal care in theUnited States is offered to an extremely diverse population with various ageranges, ethnicity’s, socioeconomic status, life-style behaviors, and motiva-tions for seeking care. The effectiveness of prenatal care cannot be analyzedin a straightforward manner because of myriad confounding factors, poten-tial selection bias, and the fact that direct randomized controlled trials ofprenatal care versus no prenatal care would be considered unethical. In hisexcellent review of current studies examining prenatal care, Fiscella [1] con-cludes, ‘‘current evidence does not satisfy the criteria necessary to establishthat prenatal care definitely improves birth outcomes.’’

In order to qualify as effective prevention, a service must identify diseaseearly, and contribute to substantial reductions in morbidity and mortality.Certainly the overall health of mothers and babies has improved dramati-cally in our country over the last century. From 1915 to 1997 the infantmortality rate declined greater than 90% to 7.2 per 1000 births and duringthe same period the maternal morbidity declined almost 99% to <0.1%reported death per 1000 live births [4]. Although organized prenatal care

Prim Care Clin Office Pract

29 (2002) 519–542

* Corresponding author.

E-mail address: [email protected] (J.H. Barash).

0095-4543/02/$ - see front matter � 2002, Elsevier Science (USA). All rights reserved.

PII: S 0 0 9 5 - 4 5 4 3 ( 0 2 ) 0 0 0 1 3 - 1

was introduced in the US during this time, so were major public health inter-ventions. Sewage disposal, safe drinking water, and the pasteurization ofmilk, as well as the earlier adoption of aseptic and antiseptic techniques inobstetrics likely contributed most heavily to this remarkable decline [2,4].

Prenatal care utilization has steadily increased in the 1980s and 1990s.Paradoxically, the rates of preterm birth, low birth weight, and maternalmortality have not improved or have worsened over this same period[5,6]. Perhaps, some may say, we have reached the limits of improvementin health outcomes given these plateaus. However, a critical appraisal ofpersistent racial and ethic disparities in prenatal outcomes provides evidencethat we have not. Currently, African American infants are more than twiceas likely to die as white infants, and African American mothers are morethan three times as likely to die of pregnancy related complications as whitewomen [6]. In their review of changing patterns of prenatal care utilizationfrom 1981 to 1995, Kogan et al [5] note that by 1995, more highly educatedwomen were likely to have ‘‘intensive utilization’’ of parental care (morethan the recommended number of prenatal visits). In an accompanyingeditorial, Misra et al [7] point out that African American and low incomewomen did not share this trend towards intensive utilization and concludethat ‘‘if groups most at risk are not experiencing increases in utilization, itis not surprising that the outcomes have changed little.’’

Recognizing the limitations of prenatal medical services, we must be com-mitted to addressing the underlying social inequities that continue to impactthe overall health and well being of our patients. It may well be that improve-ment and increases in medical intervention and technology cannot amelioratethe effects of poverty, abuse, addiction, and social chaos experienced by someof our patients. Directing our efforts towards more broad-based public healthand social change holds the potential for greater impact on health.

Preconception care

Opportunities for pre-conception prevention

To be truly ‘‘preventive,’’ prenatal care must begin even before pregnancy,as preconception care. Many key modifiable and nonmodifiable risk factorsfor poor obstetrical outcomes are present long before conception begins. Thecritical period of organogenisis occurs in the first weeks of pregnancy, oftenbefore the woman realizes she is pregnant. Of all pregnancies occurring in theUS in 1988, more than half were unintended, an equal number ending inabortion or birth, both with great social and personal consequences [8].According to the 1995 National Survey of Family Growth, 28% of USwomen have had an unintended birth [9]. One fifth of all pregnant womenand approximately half of women with unintended pregnancies do not startprenatal care during the first trimester [4]. Therefore, the burden of optimiz-ing health for pregnancy falls on the shoulders of all health care providers

520 J.H. Barash, L.C. Weinstein / Prim Care Clin Office Pract 29 (2002) 519–542

who are in contact with women of childbearing age. Additionally, othersocial and cultural institutions accessed by women of reproductive age canbe considered as potential opportunities for educational intervention [10].

While risk factors such as poverty and low educational level cannot beameliorated at an office visit, the opportunity to address other modifiablerisk factors is at least intuitively appealing. In a study of women attendingan urban family practice clinic who had a negative pregnancy test, Jack et al[11] found that 92% of the women reported at least one preconception riskfactor. However, a follow-up study failed to show that notification ofwomen and their clinicians of identified preconception risks improved theproportion of women who had risk reduction interventions [12]. Whilepreconception risk factors have been identified and described, the effective-ness of many interventions remains to be established [10,11,13]. Given thereality that many ‘‘preconception’’ issues will not be addressed until thefirst prenatal visit, we will limit the discussion in this section to thoseinterventions that are of markedly enhanced value if addressed prior toconception.

Folic acid supplementation

Of the few measures that are effective and useful, folic acid supplementa-tion ranks in the highest category. The most common neural tube defects,spina bifida and anencephaly, result in 2500 to 3000 US births annually[14]. Periconceptional supplementation with folic acid can reduce the riskof neural tube defect by more than two thirds [15]. The US Preventive Ser-vices Task Force recommends folic acid supplementation of 0.4–0.8 mg/daybeginning at least one month prior to conception and continuing throughthe first trimester. This amount is increased to 4 mg for women with a his-tory of a prior pregnancy affected by a neural tube defect (‘‘A’’ recommen-dation) [16]. Folic acid supplementation is truly a periconceptionalintervention since the neural tube closure occurs during the first four weeksof gestation, very often before pregnancy is diagnosed. Despite these recom-mendations, a 1998 poll showed that 70% of women of childbearing age arenot following these recommendations [17]. Interviews with inner city womenduring their first prenatal visit revealed that 4% reported taking a folic acidsupplement properly prior to becoming pregnant [18].

To address these discrepancies, fortification of enriched grain products inthe US was authorized by the FDA in 1996, with compliance mandatory byJanuary 1998 [14]. Since this time, substantial increases in serum and RBCfolate concentrations among women of childbearing age have occurred [19].A study by Honein et al [14] reported in JAMA in June 2001, revealed a 19%reduction in NTD birth prevalence following folic acid fortification of theUS grain supply. However the authors note that other factors includingan overall decreasing trend in NTD prevalence and birth certificate report-ing discrepancies may have contributed to this reduction.

521J.H. Barash, L.C. Weinstein / Prim Care Clin Office Pract 29 (2002) 519–542

Alcohol

Maternal alcohol use is now the leading known cause of mental retarda-tion, and fetal alcohol syndrome outranks both Down syndrome and spinabifida in prevalence [20]. The dysmorphic facial features of fetal alcohol syn-drome result specifically from ethanol exposure during the first 3 to 8 weeksof gestation [21]. Data from the National Maternal and Infant Health Sur-vey in 1988 revealed that half of all women in the study drank alcohol dur-ing the 3 months prior to pregnancy recognition, and 5% reportedconsuming 6 or more drinks per week. In this study, the strongest risk fac-tors for frequent drinking in the periconceptual period included: being asmoker, white non-Hispanic, age 25 or older, and unmarried [21]. The con-sequences of periconcpetual alcohol intake should be discussed with allwomen of childbearing age, and abstinence recommended for all womencontemplating pregnancy. Reliable screening for alcohol abuse can takeplace in the office setting. Women with identified problems should bereferred for specialized treatment.

Tobacco

According to the Smoking Cessation Clinical Practice Guideline Panel,quitting smoking prior to conception or early in pregnancy is most beneficial[22]. Smoking rates in pregnant women are approximately half that of theirnon-pregnant counterparts [23]. Pregnancy may represent an opportunityfor smoking cessation intervention; so further discussion of this topic willbe deferred until the section on first trimester intervention.

Immunizations

Several vaccine preventable infectious diseases can have tragic fetal and/or neonatal consequences if contracted perinatally. For this reason, allwomen of childbearing age should be questioned as to their immunization/exposure history regarding rubella, varicella, and hepatitis B.

Congenital rubella syndrome (CRS) occurs when a mother contractsrubella during the first trimester of pregnancy. The risk of transmission to thefetus during maternal infection in the first trimester ranges from 10% to 85%[24–26]. A review of the medical records of 21 southern California womenwho delivered infants with CRS revealed that over half of the women hadmissed opportunities for screening. These included opportunities for screen-ing during previous pregnancies, during induced abortions, and premaritalscreening [27]. Recent evidence suggests increased risk for rubella infectionand CRS in the Hispanic population, especially those born outside of theUS. Recent data also suggests that the risk for rubella infection is highestamong young adults [26]. The American Academy of Pediatrics Committeeon Infectious Disease 2000 and the Advisory Committee on ImmunizationPractices recommends that all post pubertal females be assessed for rubella


susceptibility during physical exams, family planning visits, and STD screen-ing. Women who have not received at least one dose of the vaccine, or whoare non-immune by serologic testing should be given the MMR vaccine[26,28]. Women should be counseled to avoid pregnancy during the first3 months following vaccination because of the theoretical risk of transmit-ting infection to the fetus through the attenuated live virus vaccine. However,retrospective review of 321 women who inadvertently received the MMRvaccine between 1979 to 1989 found no cases of CRS in their infants [25].

People who acquire chronic hepatitis B infection as infants or young chil-dren have a 25% risk of death due to HBV related liver cancer or cirrhosis.Chronic HBV infection occurs in up to 90% of infants born to HBeAg-positive mothers [29]. Because of these dismal statistics all women of child-bearing age with high risk sexual or drug using practices, or occupationalexposure risk should be offered the hepatitis B vaccination series. Pregnancyand lactation is not a contraindication to hepatitis B immunization.

Varicella is a highly contagious childhood disease. Approximately 90% ofpersons in the United States have acquired varicella before reproductive age.In fact, 70% to 90% of women who do not recall a history of varicella havedetectable antibodies. Nevertheless, varicella infection in pregnancy can haveserious consequences for the mother and the neonate. While varicella is anuncommon infection in adults, and probably no more common in pregnantwomen, it appears to be more fulminant, especially in the case of varicellapneumonia [24]. Because of immaturity of the neonatal immune system, andlack of maternal antibody, neonatal varicella infection is associated with ahigh morbidity rate when maternal disease develops from five days prior todelivery up to 48 hours postpartum [30]. The Advisory Committee on Immu-nization Practices recommends varicella vaccination for all women of child-bearing age without a prior history of varicella [31]. Women should beadvised to avoid conception for at least one month post vaccination.

Exposures

Based primarily on consensus and expert opinion, routine serologicscreening for CMV and toxoplasmosis is not recommended by ACOG[30]. Rather, women should be counseled to prevent exposure to CMV andtoxoplasmosis during conception and pregnancy. To limit exposure to CMVwomen should practice universal precautions and thorough hand washingwhen around young children and immunocompromised individuals. Toavoid toxoplasmosis infection, women should avoid raw and undercookedmeat, wear gloves when gardening, and avoid exposure to cat litter.

While less commonly seen in clinical practice, some agents associatedwith adverse female reproductive capacity or developmental effects include:anesthetic gases, mercury, lead, organic solvents, radiation, and vinyl chloride[32]. An occupationalmedicine specialist or occupational safety administratoris a valuable resource in determining the exposure risks in individual cases.


Maternal disease

Women with preexisting medical conditions should be carefully coun-seled to maximize pre-pregnancy health prior to conception. Diabetes mel-litus is by far one of the most commonly encountered conditions wherepreconceptional intervention is critical. Congenital anomalies are the lead-ing cause of perinatal mortality in infants of diabetic mothers. The incidenceof congenital anomalies is directly related to the degree of glycemic controlduring conception and organogenisis. Miller and co-authors [33] reported arate of congenital anomalies of 22% in women with HgA1C of greater than8.5 in the periconceptual period. Nevertheless, several recent studies suggestthat optimal periconceptional glycemic control is not occurring in clinicalpractice [34,35]. Rodgers and Rodgers [35] reported that 73% of diabe-tic women did not plan their pregnancies. Casele and Laifer [36] found thatwomen who were not advised to achieve a specific target HgA1C andglucose level were much more likely to enter pregnancy with sub-optimalglycemic control. One practical step may be to include an area forpreconception counseling in standard diabetic flow sheets used in outpatientoffices. Key components of preconceptual evaluation of the diabetic patientare outlined in the following list:

Pre conceptual evaluation of the Diabetic Patient- Key Components [37]Medical/ObstetricHistory

duration and type of diabetesacute and chronic complications of diabetesdiabetes medication useself monitoring of blood glucosephysical activityconcomitant medical conditionspregnancy history, including complicationssupport system

Physical Examblood pressuredialated retinal examinationcardiovascular examinationneurological examination for autonomic neuropathy

Laboratory evaluationHgA1Cserum creatinine24 hour urine proteintsh (for Type 1 DM)

Initial Mangement PlanReferral to multidisciplinary care team if availableCounseling about risks and prevention of congenital anomalies andobstetrical complications


Consultation with maternal fetal medicine specialist if availableSelection of anti-hyperglycemic therapyEstablishment of plan to achieve low-risk glycemia (less the 1% above thenormal range)

Other maternal conditions which benefit significantly from preconceptualinterventions include: hypertension, asthma, seizure disorders, thromboem-bolic disease, autoimmune conditions, thyroid disorders, renal disease, car-diac disease, pulmonary disease, and phenylketonuria. If the mother’scondition is under control and stabilized using medications that are safein pregnancy, she can be realistically reassured. However, most women withthese conditions will benefit from preconception referral to a maternal-fetal-medicine specialist for a more in depth discussion of the impact of preg-nancy on her health and the likelihood of neonatal complications.

Genetics

There are distinct advantages to assessing genetic risk before a coupleattempts to conceive, outside of the emotional context of an already estab-lished pregnancy [38]. Patients with a specific indication for genetic testingsuch as maternal age greater than 35, family history of a genetic disease,or history of a previously affected pregnancy should be referred for geneticcounseling. Screening for heterozygote status is also appropriate in severalethnic groups including: Tay-Sachs screening in Ashkenazic Jews, sickle celldisease in African-Americans, and thalessemia in people of South East Asianor Mediterranean descent. Once genetic risk has been assessed, couples maymake informed decisions regarding reproduction and prenatal genetic eval-uation through chorionic villus sampling (CVS) or amniocentesis. ACOGhas concluded that CVS performed at 10 to 12 weeks of gestation is a rela-tively safe and accurate procedure and may be considered an acceptablealternative to second trimester amniocentesis [39]. The risk of miscarriageis 0.5% to 1% for CVS and 0.25% to 0.50% for amniocentesis [40].

Reproductive history

A review of prior poor obstetrical outcomes is best prior to pregnancy.Some conditions such as uterine malformations, maternal autoimmune dis-ease, endocrine abnormalities, and genital infection may be amenable tointervention and lessen the chance of recurrent pregnancy loss [38]. Womenwith prior history of preterm birth are at an approximately 2.5 foldincreased risk for recurrence [41]. The prevention of preterm birth remainselusive despite numerous educational and technological interventions [42–44]. However, recent data suggests that monitoring of cervical length andfetal fibronectin may be useful in identifying women with a history of pre-term birth at increased risk for recurrence [45].


First trimester

Importance of early prenatal care

Although many components of risk assessment and risk reduction duringpregnancy are most beneficial if begun during the preconception period, forthe majority of US women this process will begin at the recognition of preg-nancy, in the first trimester. For this reason, resources have been directedtowards increasing access to early prenatal care towards those populationsat highest risk for perinatal morbidities. These efforts have met with somesuccess; since 1990, the proportion of African American infants whose moth-ers entered prenatal care in the first trimester rose 19 percent, and amongHis-panics 22% [46]. The Healthy People 2010 target is to increase the proportionof all women who receive prenatal care in the first trimester from a 1998 base-line of 83% to a goal of 90% [46]. This section will review the various care andscreening modalities recommended in the first trimester designed for earlyidentification of pregnancy complications. Obviously, all the issues coveredin the previous section on preconception counseling are also applicable,although sometimes less effective, to the first trimester of prenatal care.

Initial prenatal laboratory screening

This section will examine the standard battery of laboratory testing rou-tinely ordered at the first prenatal visit as part of risk assessment in the firsttrimester, including screening for: blood type and antibody, anemia, rubella,cervical dysplasia, syphilis, gonorrhea, chlamydia, asymptomatic bacteruria,hepatitis B, and HIV. In Table 1 we report the category of evidence for eachintervention based on recommendations from the US Preventive ServiceTask Force, the American College of Obstetrics and Gynecolgy, and theCochrane Database.

Domestic violence

The prevalence of domestic violence against pregnant women rangesfrom 1% to 20% [58]. Numerous pregnancy complications including miscar-riage, premature birth, low birth weight, infection, second and third trimes-ter bleeding, and fetal injury occur with increased frequency in women whoexperience domestic violence [59,60]. Higher prevalence rates of domesticviolence are found in studies that use validated assessment instruments andin-person interviews, rather than relying on single item responses on selfreports [61]. Domestic violence (DV) patterns may change throughout preg-nancy. A review by Gazmararian [58] revealed higher prevalence rates ofdomestic violence in those studies that asked about DV more than onceduring the pregnancy, or asked during the third trimester. Other opportuni-ties for screening occur when women present with acute concerns such asabdominal pain, vaginal bleeding, or depression.


Tobacco cessation

Exposure to tobacco during the prenatal and postnatal period is the lead-ing causes of morbidity and mortality among children according to a recentreport in JAMA [23]. US data from 1996 suggest a decrease in prevalenceof smoking during pregnancy to 14%, however this apparent decline maybe influenced by strong pressures felt by women to deny tobacco use in theclinical setting [22]. Giving women the opportunity to indicate that theyhave cut down on their smoking during questionnaire or interview may in-crease likelihood that a woman will disclose her smoking status. The prenatalperiod may represent an opportunity where women are more amenableto attempt a change in smoking behavior, however it may also be a time ofincreased stress. A recent review of evidenced based intervention to promotesmoking cessation indicate that a brief 5 to 10 minute counseling sessionmay increase validated smoking cessation in up to 70% of pregnant smokers[22]. ACOG guidelines advocate the use of the 5 step ‘‘Ask, Advise, Assess,Assist, Arrange’’ clinical practice guideline as adapted from the US PublicHealth Service [62]. Advice on the use of nicotine replacement in pregnancyremains cautionary. The smoking cessation clinical practice guideline pub-lished in JAMA in 1996 states ‘‘Nicotine replacement therapy should beused during pregnancy only if the increases likelihood of smoking cessation,with its potential benefits, outweighs the risk of nicotine replacement andpotential concomitant smoking’’ [63]. A randomized controlled study ofnicotine patches for pregnant women who smoked more than 10 cigarettesa day done in Denmark concluded that ‘‘nicotine patches had no influenceon smoking cessation during pregnancy’’ [64]. Rates of postpartum smokingrelapse are high. Upwards of 70% of women who quit smoking during preg-nancy have resumed smoking by 6 months postpartum [22]. Interventionalapproaches to help decrease rates of relapse are being developed.

The second trimester

Ongoing assessment/early diagnosis of pregnancy complications

The second trimester remains an important time for the prenatal careprovider to provide ongoing preventive counseling, as well as recognizepotential pregnancy complications.

The triple screen

Screening for genetic abnormalities has become an important aspectof prenatal care. The Triple Screen, a maternal blood test that measurescirculating levels of alpha-fetoprotein (AFP), estriol, and human chorionicgonadotropin (hCG), attempts to identify women who may be at increasedrisk for carrying a fetus with a neural tube defect, Down Syndrome, and


Table

1

Initialprenatallaboratory

screeningrecommendationcomparison

Test

RatingUSPSTF

ACOG

Cochrane

Comments

BloodTypeand

antibodyscreen

‘‘A’’[16]

Recommended

[47]

Administrationofanti-D

at

28wksreducesincidence

ofalloim

unizationfrom

1.5%

to0.2%

without

adverse

effect[48]

See

secondtrim

estersection

forfurther

discussion

Hem

oglobin/hem

atocrit

‘‘B’’atfirstprenatalvisit,

‘‘C’’forrepeattestingin

asymptomaticlow

risk

women

[16]

Recommended

atfirst

prenatalvisitandagain

earlyin

thirdtrim

ester

[49]

Inconclusiveevidence

on

theeffects

oftreatingiron

deficiency

anaem

iain

pregnancy

dueto

the

shortageofgoodquality

trials[50]

Rubella

screening

‘‘B’’[16]

Recommended

[51]

Notspecificallycovered

USPSTFrecommend

screeningforrubella

vaccinationbyhistory

or

serologyatthefirst

clinicalencounterforall

women

ofchildbearing

age.

Pregnantwomen

foundto

benonim

mune

should

becounseledto

avoid

exposure

and

immunized

postpartum.

See

preconceptioncare

sectionfordetailed

discussion

Papanicolaoutest

‘‘A’’[16]

Recommended

[52]

N/A

Prenatalcare

mayrepresent

aopportunityfor

screening


RPR

‘‘A’’[16]

Recommended

[49]

N/A

Both

USPSTFandACOG

recommended

repeat

screeningin

thethird

trim

esterandatdelivery

forhighrisk

populations.

Gonorrhea

and

Chlamydia

Screening

‘‘B’’forhighrisk

women

‘‘C’’foruniversal

screeningofpregnant

women

[16]

Recommended

forhigh

risk

women

[49]

N/A

Highrisk

population

includewomen

under

25

with2ormore

sexual

partnersin

thepast

year,

women

withaprior

history

ofgonorrhea

infection,andcommercial

sexworkers(prostitutes).

Additionaltestingin

the

thirdtrim

esteris

recommended

forwomen

atcontinued

risk

for

infection

Screeningforasymptomatic

bacteruria

‘‘A’’forscreeningwith

urineculture

[16]

Recommendsdipstick

urinalysiswithfollow-up

confirm

atory

culture

[53]

Antibiotictreatm

entis

effectivein

reducingthe

risk

ofpyelonephritisin

pregnancy

[54]

Pregnantwomen

with

asymptomaticbacteruria

are

more

likelyto

acquire

symptomaticinfection

andpyelonephritis.Meta-

analysisbyRomeroet

al

confirm

edthe

relationship

between

untreatedbacteruriaand

low-birth

weightand

preterm

birth

[55]

(continued

onnextpage)


Table

1(continued

)

Test

RatingUSPSTF

ACOG

Cochrane

Comments

Hepatits

BScreening

‘‘A’’[16]

Recommended

[38]

N/A

USPSTFandACOG

recommendrescreening

inthirdtrim

esterfor

women

athighrisk

for

exposure

HIV

screening

‘‘A’’forwomen

atincreased

risk

forinfectionand

those

from

communities

withincreasedprevalence

ofseropositivenew

borns

(eg,>0.1%)‘‘C’’for

universalprenatal

screeningin

low

risk

communities[16]

Supportsthe

recommendationofthe

Institute

ofMedicinefor

universalscreeningasa

routinecomponentof

prenatalcare

[56]

Zidovudine,

nevirapineand

deliverybyelective

caesareansectionappear

tobeveryeffectivein

decreasingtherisk

of

mother-to-child

transm

issionofHIV

infection[57]


certain other chromosomal abnormalities. Counseling about the risksand benefits of this test must be done prior to testing. Pretest counselingshould emphasize that: (i) it is a screening test and is not diagnostic, (ii) anormal test is reassuring but not absolute, and (iii) an abnormal test indicatesthe need for further testing. Although a women may choose not to undergothe test, The United States Preventive Services Task Force recommendsoffering the test to all women between 15 to 18 weeks [16].

Ultrasonography: the 20-week ‘‘screening’’ ultrasound

Although the standard of care in many large cities is to offer all women aroutine screening ultrasound at 18 to 20 weeks, no benefit of this practice hasbeen proven [65]. On the other hand, the selective use of ultrasound for spe-cific indications has been beneficial to answer specific clinical questions.

Selective ultrasonography can provide valuable information in many clin-ical situations. It has great accuracy in predicting gestational age in the firsttrimester if the patient is unsure of her last menstrual period or conceived onoral contraceptives. It can rapidly predict the presence or absence of fetallife or multiple gestation. It is relatively accurate in identifying certain fetalanomalies if clinical suspicion is present. It can locate placental position ifthe clinician is concerned about placenta previa. Interval growth can beassessed if the provider is concerned with growth restriction. Amniotic fluidlevel is easily calculated if oligohydramnios or polyhydramnios is suspected.While there certainly is great value in using ultrasound selectively, it there-fore does not follow that offering screening ultrasound to all women wouldbe worthwhile and cost-effective [66].

Routine early ultrasound (in the first trimester) has been shown to reducethe rate of induction for post-term pregnancy, presumably because of bettergestational age determination. While this knowledge can decrease the cost ofcare associated with induction, fetal outcome has not been shown toimprove [67]. Routine late ultrasonography has not been shown to decreaseperinatal morbidity and mortality, but does offer much more anatomicaldetail. Historically, prenatal care providers usually offer a screening ultra-sound to their patients between 18 to 20 weeks in order to pick up as manyanomalies as possible, with the hope of offering it at an early enough time togive women choices if an anomaly should be identified [66].

Diet and nutrition

The relationship between maternal nutritional intake and fetal well-beingis not well-known. There have been a number of observational studies look-ing at this issue, but they are often confounded by factors such as educa-tional, economical, or social constraints. It is known that severe dietaryrestriction, as during a famine, can cause a marked decrease in birthweight.


Trials of dietary restriction in women with excessive weight gain have shownthat fetal growth is impaired, although it is not known what effect this hason perinatal morbidity and mortality. There is no data to support that diet-ary restriction in pregnancy benefits mother or fetus [15].

While nutritional advice appears effective in increasing a pregnant wom-an’s energy and protein intakes, the implications for fetal, infant, and mater-nal health are indeterminate from the available trials [68]. Although moreresearch is needed in this area, it is clear that no woman should go withoutadequate nutrition, as well as access to valid nutritional information.Furthermore, all low-income women should be referred to the government-sponsored Women, Infants, and Children (WIC) food program, whichprovides food stamps and nutritional counseling.

Screening for ‘‘gestational diabetes’’

‘‘Gestational Diabetes’’ (GDM) is characterized in the 1994 ACOGTechnical Bulletin as ‘‘the onset or recognition of glucose intolerance duringpregnancy’’ [69]. It is thought that about 50% of these women will developovert diabetes within 20 years. Based on retrospective studies, it has been his-torically thought that treatment of GDM may decrease perinatal morbidity,including macrosomia and subsequent birth trauma, fetal hypoglycemia, aswell as need for cesarean section. In contrast, an analysis of prospective stud-ies performed by the Cochrane Database argues that there is not enoughevidence to support routine screening for GDM [70].

Screening for GDM is usually offered to women between 24 to 28 weeksof gestation. A 50-gram load of glucose is consumed by the patient withoutregard to fasting, and 1 hour later her serum glucose level is determined. Athreshold of 140 mg/dl has been thought to correctly identify 90% of cases.If this initial test is elevated, the patient is then offered a 3-hour 100-gramglucola challenge for confirmation, with measurement of ‘‘fasting’’, 1-hour,2-hour, and 3-hour glucose values. The test is considered positive if morethan one of the serum levels is abnormal when compared to standardizedlevels (Fasting: 105 mg/dl, 1-hour: 190, 2-hour: 165, 3-hour: 145) [71].

Following the diagnosis of gestational diabetes, it is generally recom-mended that the patient be placed on the same diet that women with pre-existing diabetes adhere to. Fasting and 2-hour post-prandial glucose levelsare monitored closely, and if blood sugars remain consistently high, insulinis initiated.

Analysis of the small number of randomized, controlled studies shows nobenefit of dietary therapy in reducing perinatal morbidity or rate of cesareansection [72]. Until more conclusive studies are completed, the American Col-lege of Obstetrics and Gynecology recommends routine screening at 24 to 28weeks of gestation, earlier if the woman has risk factors for developing dia-betes [69].


Rhesus isoimmunization

The reduction in the incidence of Rhesus isoimmunization is a prototypefor the effectiveness of prenatal care. Prior to the advent of anti-D immuno-globulin in early 1970s, upwards of 10% of all pregnancies were affected byhemolytic disease of the newborn, and it was a major cause of perinatalmorbidity and mortality. If anti-D is given at the appropriate time and atthe appropriate dose, the risk of developing rhesus isoimmunization isdecreased to 0.1% [47].

Women who are RhD-negative are at risk for developing antibodies tothe Rh antigen if any Rh-positive fetal cells enter the maternal circulation.Once sensitized, any subsequent Rh-positive fetus that is carried by thepatient is at increased risk of severe hemolysis caused by maternal anti-bodies directed at the fetal cells.

The most common time for fetal cells to enter the maternal circulationis during birth. However, fetomaternal transfusion can occur with spon-taneous or induced abortion, even in the first trimester, as well as anyform of uterine bleeding, including abdominal trauma, placenta previa, orplacental abruption. Bleeding from the fetus to the mother’s circulation hasalso been documented during such pregnancy-related procedures aschorion villus sampling, amniocentesis, and external version of a breechpresentation.

Based on good and consistent scientific evidence, the unsensitized RhD-negative women should receive anti-D immunoglobulin at approximately 28weeks of gestation, and again within 72 hours after the delivery of an RhD-positive infant. She should also receive immunoglobulin after any pregnancyloss, as well as after any invasive procedure (ie, amniocentesis). While theevidence is not as strong, many providers would offer prophylaxis for athreatened miscarriage, second- or third-trimester bleeding, or abdominaltrauma [48].

Anemia

Iron deficiency anemia is more common in pregnancy because of mater-nal blood volume expansion (especially in the second trimester), fetal ironneeds, and blood loss during delivery. This increased demand for iron canusually be met by dietary intake of iron. Iron supplementation has becomeroutine in this country, and while this supplementation may improve hem-atologic indices, it has not been proven in controlled trials to improve eithermaternal or fetal clinical outcomes [73]. Nonetheless, one can theorize thatpreventing low hemoglobin at term would lower the need for transfusiondue to blood loss at delivery, and minimize the risks associated with bloodtransfusions. Further studies are needed to clarify whether routine iron sup-plementation in well-nourished populations improves fetal and maternaloutcomes.


The third trimester

Maximize opportunity for safe and timely labor and birth

Three important third-trimester areas that impact both mother and fe-tus are preterm labor, Group B streptococcus (GBS), and the post-termpregnancy.

Preventing preterm labor

Preterm labor is defined as labor beginning before 37 weeks gestation,with more serious consequences occurring before 34 weeks gestation.Unfortunately, preterm birth rates have not changed over the past fortyyears [74]. Because preterm birth continues to be a major cause of morbidityand mortality, prevention and treatment of preterm labor is important.

In most cases, the cause of preterm labor is unknown [74]. There is astrong association between a woman’s risk of preterm birth and low socio-economic status, extremes of maternal age, and low prepregnancy weight.Certain maternal behaviors, such as smoking and cocaine use, correlate sig-nificantly with preterm delivery. One study showed that women who do notseek prenatal care, regardless of socioeconomic statues, are at increased riskof delivering preterm, although its unclear which aspects of prenatal carereduce this risk [75]. The risk of preterm birth is also associated with thenumber of prior preterm births a woman has had.

Genital tract infections, such as GBS, Neisseria gonorrhoeae, chlamydia,and trichomonas, have been implicated as a risk for preterm delivery, buttheir exact contribution remains ill-defined. The practice of obtaining ante-natal cultures is more for the prevention of perinatal transmission ratherthan the prevention of preterm birth.

Risk-scoring systems, developed to help predict women likely to deliverpreterm, have demonstrated varying degrees of success. Overall, the sensitiv-ity of such systems is less than 50%, and the positive predictive value hasbeen less than 20%. Certain markers, such as the identification of fetal fibro-nectin (a normal constituent of the extracellular matrix of the maternal-fetalinterface) measured in the posterior fornix of the vagina, hold promise asindicators of developing premature labor. A recent meta-analysis reportsthat among patients with symptoms of preterm labor, fetal fibronectinappears to be among the most effective predictors of preterm delivery (sen-sitivity 89%, specificity 86% for delivery within 7 days). Fetal fibronectin isless effective in predicting preterm birth in the asymptomatic patient [76].

Other interventions, such as cervical cerclage, home uterine-activity mon-itoring, bed-rest, and routine cervical assessment by vaginal exam and ultra-sound, have unfortunately not been demonstrated to be effective for theprevention of preterm birth [77].

Some clinicians have recommended prescribing medications to preventpreterm contractions in women who are considered to be at increased risk


of preterm delivery. Trials of betamimetic drugs to prevent preterm laborhave demonstrated no overall benefit [74,77]. However, if active pretermlabor is arrested in a patient, then there is some evidence that tocolyticagents may be beneficial in temporarily postponing delivery, allowing trans-fer of a mother to a medical center equipped with a neonatal intensive careunit, or allowing treatment with corticosteroids to reduce neonatal morbid-ity. Still, there is no evidence that these drugs improve long-term perinatalmorbidity and mortality [74].

Fetal growth restriction

Perinatal morbidity and mortality is increased in the presence of growthrestriction. Fetal growth is most commonly estimated by fundal heightmeasurement, the distance between the pubic symphysis and the uterine fun-dus. While there is considerable inter- and intra-observer variation with thismethod, several studies have proven that it has good sensitivity and specif-icity for predicting low birthweight for gestation. While low birthweightdoes not necessarily reflect growth restriction, fundal height measurementis useful as a screening test for further evaluation [78].

Fetal growth restriction is best estimated by comparing two or moremeasurements of size calculated 3 to 4 weeks apart (looking at the intervalgrowth), rather than as an individual weight compared with a median birth-weight at a certain gestational age [79]. Fetal growth restriction is usuallyassociated with placental malfunction, or inadequate blood supply to theplacenta. Risk factors associated with growth restriction include maternalmedical conditions, such as hypertension or diabetes, genetic disorders, mal-nutrition, and smoking and substance abuse.

While avoidance of smoking during pregnancy has had a positive effecton birthweight, randomized controlled trials have found few other interven-tions beneficial in preventing or treating intrauterine growth restriction(IUGR) [80]. Antihypertensive therapy, calcium or zinc supplementation,maternal oxygen therapy, or aspirin therapy have not been shown to beeffective with respect to IUGR. Once IUGR has been diagnosed, the useof Doppler ultrasound to measure umbilical artery waveforms has beenshown to reduce perinatal death, and should be used as part of the evalua-tion [81]. Doppler velocimetry has not been as a screening tool [80].

The growth-restricted fetus should be delivered when the risks of fetaldeath exceeds that of neonatal death. This decision is often based on non-reassuring fetal assessment or a complete cessation of fetal growth assessedby ultrasound over a 2 to 4 week period.

Tocolysis with betamimetic drugs has become widespread in clinical prac-tice when there is concern with the fetal status during labor. The theory isthat uterine relaxation improves uteroplacental blood flow, thereby increas-ing fetal oxygenation. Although persistent fetal heart rate abnormalities arereduced with tocolyis, perinatal outcome has not been demonstrated to


improve. Further studies are needed to find out if tocolysis is beneficial forimproving outcomes in the growth-restricted fetus.

Group B streptococcus

GBS is the most frequent cause of sepsis in neonates. The incidence isapproximately 2 per 1000 live births, and is related to the density of mater-nal colonization at birth. Prevention of transmission has focused on admin-istration of antepartum and intrapartum antibiotics, since prophylaxisnewborns may be too late. It appears that intrapartum antibiotic treatmentof women colonized with GBS reduces neonatal infection [82].

The optimal method for determining which women should receive intra-partum antibiotics has been debated. Recently, the AAP and ACOG devel-oped a consensus opinion with the aid of the CDC [83]. Screening can becarried out by the ‘‘risk-based method’’ or ‘‘screening-based method’’. In therisk-based method, all women with risk factors are treated in labor with pen-icillin, without regard to a culture result. These include women in pretermlabor, intrapartum fever >38�C, or prolonged rupture of membranes >18hours. In the screening-based method, all women at approximately 35 weeksreceive a screening culture, and are treated in labor if it is positive. Regard-less of the screening method chosen, women with GBS bacteriuria duringpregnancy should be treated at the time of diagnosis. Because these womenare felt to be heavily colonized, they should also be treated with intrapartumantibiotics during labor. Intrapartum antibiotics should also be adminis-tered to women who have previously given birth to an infant with invasiveGBS disease [84].

Penicillin G is the drug of choice for intrapartum prophylaxis (5 millionU initially and then 2.5 million U every 4 hours). Ampicillin is an acceptablealternative (2 g initially and then 1 g every 4 hours), but is less desirablebecause it has a broader spectrum and is therefore more likely to lead toselection of resistant organisms. Intravenous clindamycin is an acceptablechoice for women allergic to penicillin [84].

Post-term pregnancy

Post-term pregnancy, defined as pregnancy lasting more than 42 weeks, isassociated with an increase in perinatal mortality and early neonatal convul-sions. The most common cause for post-term pregnancy is inaccurate dat-ing, which is now decreasing with the advent of routine early ultrasoundfor gestational age determination [67].

In some cases, post-term pregnancy can be avoided by sweeping the mem-branes (digital separation of the fetal membranes from the lower pole of theuterus) at or beyond 40 weeks [85]. Membrane sweeping has not been shownto increase infection or affect the mode of delivery, but can cause increaseddiscomfort for the woman. Presently, there is insufficient data to recommendbreast and nipple stimulation to prevent post-term pregnancy [86].


Because of the small but significant increase in perinatal mortalityin post-term pregnancy, various recommendations have evolved for careof this subset of patients, from induction at 40, 41, or 42 weeks gesta-tion, to selective induction based on outcomes of fetal testing, to an inten-tion to allow for spontaneous labor. Meta-analysis of 19 randomized trialsdemonstrate that induction at 41 weeks reduces the risk of perinatal death,at a rate of one death saved from 500 inductions. Furthermore, with ap-propriate induction methods, such as the use of prostaglandins for cervicalripening, there is a small but significant decrease in the risk of cesarean sec-tion. The above findings were not true for pregnancies between 40 and 41weeks [86].

Fetal surveillance is usually recommended after 40 weeks to identify anyfetal compromise. No single surveillance protocol for monitoring fetal well-being in post-term pregnancy appears to be superior. Furthermore, there isinsufficient evidence that testing improves outcomes [87].

Summary

Advances in preconception and prenatal care have been successful inreducing risk in a number of areas. Folic acid supplementation, abstinencefrom alcohol, tight glycemic control in pre-gestational diabetics, and theadministration of rhogham all have been successful in reducing individualrisks. Unfortunately, overall perinatal morbidity and mortality has notdecreased in the past two decades. In light of this, clinicians must remainabreast of the latest research and technological advances, and adopt thosepractices that improve outcomes. Continued critical appraisal of persistentracial and ethnic disparities may be useful in understanding and reversingcurrent trends. Additionally we must continue to creatively develop instru-ments of quantifying those aspects of high quality prenatal care, whichare unmeasurable. Furthermore, we must advocate on a local, state, andnational level for improved services for our prenatal patients not just in theoffice and the hospital, but in their homes and communities.

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