Hospital Use and Health Status ofWomen during the 5 Years followingthe Birth of a Premature,Low-Birthweight Infant

Jennifer S. Haas, MD, MSPH, and Marie C. McCormick, MD, ScD

BackgroundDespite having one of the most

advanced medical care systems in theworld and nearly universal health insur-ance coverage for medical care duringpregnancy, the United States continues tohave one of the highest rates of infantmortality.' Advances in neonatal carecontinue to increase the limits of viabil-ity,2 but the smallest survivors havesignificant long-term health and develop-mental problems.3 Despite the improvedsurvival of premature, low-birthweightinfants, the rate of preterm delivery hasremained stable.4 Improved access toprenatal care has not led to improvementsin the rate of preterm delivery or very lowbirthweight,5-7 in part because little isknown about the causes of pretermdelivery.

Women who have delivered a prema-ture, low-birthweight infant are at in-creased risk of having a subsequent poorbirth outcome.8 This "continuity of risk"suggests that more attention should bepaid to maternal health status beyond thetraditional prenatal period. Interventionsdirected solely at improving the health ofpregnant women may fail to improvematernal or infant health status, perhapsbecause the prenatal period is too late toimprove maternal health and health behav-iors. Access to health care beyond theprenatal period may be particularly lim-ited for disadvantaged women, who are atincreased risk of adverse pregnancy out-comes.8'9 Since interpregnancy may be awindow of opportunity to improve thehealth status of these high-risk women, itis critical to understand the subsequenthealth problems and health care needs ofwomen with a history of a premature,low-birthweight infant.

To better understand the health statusof women who have had an adverse birth

outcome, we examined subsequent healthstatus and use of hospital services for acohort of women during the 5 yearsfollowing the birth of a premature, low-birthweight infant.

MethodsSample

Women who gave birth to a prema-ture, low-birthweight infant and whoenrolled in the Infant Health and Develop-ment Program, a multisite, randomizedtrial of a comprehensive early interven-tion program designed to reduce thedevelopmental and health problems ofthese infants, were eligible for this study.The study design, enrollment criteria,recruitment procedures, and interventionprogram have been described in detailelsewhere'015 and are summarized below.

Consecutive infants who were bornat one of the eight participating centers,who would reach 40 weeks' postconcep-tional age from January 7, 1985, throughOctober 9, 1985, whose birthweight wasless than 2500 grams, whose gestationalage at birth was 37 weeks or less, and whodid not fit predefined exclusion criteriawere eligible to participate. Reasons for

At the time of the study, Jennifer S. Haas waswith the Division of General Medicine, Depart-ment of Medicine, Brigham and Women'sHospital, and Harvard Medical School, Boston,Mass. Marie C. McCormick is with the Depart-ment of Maternal and Child Health, HarvardSchool of Public Health, and the Joint Program inNeonatology, Department of Pediatrics, HarvardMedical School.

Requests for reprints should be sent toJennifer S. Haas, MD, MSPH, Division ofGeneral Internal Medicine, San Francisco Gen-eral Hospital, 1001 Potrero Ave, Box 1364, SanFrancisco, CA 94110.

This paper was accepted September 9,1996.

American Journal of Public Health 1151

Hans and McCormick

exclusion prior to randomization includedresidence outside of the geographic catch-ment area, being a sibling of an eligibletwin, death prior to recruitment, a moth-er's inability to participate in an interven-tion program in English, and a maternalreport of drug, alcohol, or psychiatrichospitalization.'5 Seventy-six percent ofthe eligible infants were enrolled in thestudy.'5 The eight sites were chosen toreflect different geographic regions anddemographic populations and consisted ofthe University of Arkansas, Albert Ein-stein College, Harvard University, theUniversity of Miami, the University ofPennsylvania, the University of Texas, theUniversity of Washington, and Yale Uni-versity. The early intervention programwas initiated at the time of the infant'shospital discharge and continued until 36months of age (corrected for the duration

of pregnancy). The intervention consistedof home visits and child attendance at a

child development center.0 '11

This analysis is based on the 985mothers of the target infants. All inter-views were conducted in English, al-though not all women used English as

their primary language. Retention in thestudy was high; follow-up data were

available on 870 (88.3%) of women

through 5 years.

Assessment

Each mother and her child were

assessed by study staff at 40 weeks ofconceptional age and at 4, 8, 12, 18, 24,36, 48, and 60 months. At each assess-

ment, data were collected from the motherabout her hospital use and reasons forhospitalization. Each woman was alsoasked to rate her overall health statusduring the past year on a 5-point scaleranging from poor to excellent. All of themeasures presented in this analysis are

based on maternal self-report.

Analytic Variables

We focused our analyses on twooutcome measures: (1) a maternal healthrating of poor or fair (i.e., poorer health) 5years after the delivery and (2) maternalhospital use during this period, particu-larly for a non-pregnancy-related condi-tion.

Independent variables examined were

age; race (African American, Hispanic,White/other); level of education at thetime of the child's birth (did not completehigh school, completed high school);self-reported health status at the time ofthe child's birth (poor/fair, good/verygood/excellent); insurance status (private/managed care, Medicaid, uninsured); mari-tal status (married, unmarried); parity(primiparous, multiparous); current em-

ployment status (employed, unemployed);current education status (in school, not inschool); current household income (lessthan $10 000 per year, at least $10 000 peryear); current cigarette use (any, none);current alcohol or drug use (any, none);current mental healthl6; and preexistingmedical or obstetrical conditions, includ-ing chronic hypertension, pregnancy-related hypertension, diabetes mellitus(gestational or chronic), asthma, andobesity. We also included two measures ofthe infant's health status: very low birth-weight (< 1500 g) and the mother'srating of her child's general health sta-tus.'7 The effects of the study site andparticipation in the intervention group on

maternal health and subsequent hospitaluse were also assessed.

Analysis

Our analysis was designed to exam-ine factors associated with poor maternalhealth status and subsequent hospital use

among a cohort of women with a prema-

ture, low-birthweight infant. First, descrip-tive statistics were used to examine thefrequency of poor or fair health and theoverall rate of hospitalization as well asthe rate of hospitalization for non-

pregnancy-related indications. Second, a

proportional hazards model,18 using a

forward selection algorithm, was used toidentify the associations of the indepen-dent variables with subsequent maternalhospitalization. Since these models were

exploratory, we used an entry criterion ofP < .25, with variables remaining in themodel having a P < .15. These modelsalso controlled for maternal age, race,participation in the intervention group,and study site. We report 95% confidenceintervals for the adjusted relative ratesfrom the proportional hazards models.Finally, logistic regression was used toexamine the independent association be-tween the potential predictor variablesand poorer maternal health status at 5years. Again, a forward selection algo-rithm was used with similar entry and exitcriteria. We report 95% confidence inter-vals for the adjusted odds ratios. SASsoftware was used for all analyses.'9

ResultsTable 1 presents the sociodemo-

graphic characteristics of the study sam-

ple at the time of enrollment. Many of thewomen had medical problems duringpregnancy: 16.5% had pregnancy-relatedhypertension, 3.2% had chronic hyperten-sion, 2.9% had diabetes, and 2.6% hadasthma.

By the fifth year after giving birth,59.3% of the women had been hospital-ized. Pregnancy was the most common

cause of hospitalization, but the rates ofhospitalization for a non-pregnancy-related indication within the 5-year periodwere also substantial, with 29.7% ofwomen being hospitalized for such an

indication.The most common causes of non-

pregnancy-related hospitalizations were

genitourinary tract (23%), respiratory(19%), and gastrointestinal problems(14%) and injury (12%). Genitourinaryproblems included ovarian cysts (27%),

1152 American Journal of Public Health

TABLE 1-Description of theStudy Sample atEnrollment: Women(n = 985)Participating in aMultisite EarlyIntervention Trialafter the Birth of aLow-Birthweight,Premature Infant

No. %

RaceWhite 329 33.4African American 517 52.5Hispanic 105 10.7Other 34 3.5

Insurance statusUninsured 251 25.5Medicaid 385 39.1Private/managed 349 35.4

careEducation< highschool 394 40.0High school 270 27.4graduate

Some college 321 32.6Income< $10 000 329 36.9$10 000-$19 999 216 24.2$20 000-$49 999 273 30.6$50 000+ 74 8.3

Married 455 46.2Cigarette use 346 35.1Alcohol use 128 13.0Drug use 38 3.9

Note. Mean age was 25 years, with arange of 13 through 43 years. Meanparity was 1, with a range of 1 through10.

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Maternal Health after Premature Birth

urinary tract infections (25%), uterinedisorders (17%, including adhesions andendometrial hyperplasia), and pelvic in-flammatory disease (10%). Respiratoryproblems included pneumonia (43%),asthma (29%), and tonsillitis (25%).Gastrointestinal problems included gall-stones (23%), appendicitis (23%), colitis(19%), and hernias (15%).

The strongest factor associated withany hospitalization during the 5 years

following the birth of a low-birthweight,premature infant was subsequent preg-

nancy (Table 2). Women who reportedthemselves to be currently in poorer

health were also more likely to behospitalized in a given year, and thisfactor was associated with hospitaliza-tions for non-pregnancy-related indica-tions (Table 3). Women with a history ofasthma were also at increased risk ofhaving a hospitalization for a non-

pregnancy-related indication.Five years following the birth of a

premature, low-birthweight infant, 16.9%of women reported themselves to be inpoor or fair health. The factors signifi-cantly associated with being in poorer

health 5 years following the deliveryincluded the number of intervening years

in poorer health, more than 1 year ofpoverty, and a history of obesity (Table 4).Women with more than 1 year of employ-ment were less likely to be in poorer

health.

DiscussionOur work suggests that women who

have had a premature, low-birthweightinfant experience substantial morbiditythat continues for at least 5 years follow-ing the birth of the child. Almost 60% ofthese women required hospitalization dur-ing this 5-year period. While pregnancy

accounted for approximately half of thesehospitalizations, the remainder were unre-

lated to pregnancy. Almost 20% of thesewomen reported themselves to be in poorto fair health.

Several factors were associated withpoor health outcomes among women whohad delivered a premature, low-birth-weight infant. Self-reported poor or fairhealth was strongly associated with subse-quent hospital use, both overall and forconditions not related to pregnancy.Women who experienced persistent pov-erty or who were obese were more likelyto report poorer health status. Continuousemployment and health insurance were

associated with improved health status.While women who participated in this

intervention trial have previously beenshown to be employed for more monthsand to receive more public health insur-ance 3 years following the birth of theirchild,14 participation in the interventiongroup did not affect subsequent healthstatus or hospital use at 5 years.

Our findings are consistent withprior work that examined the rate ofhospitalization during the year followinga delivery among disadvantaged women

in central Harlem.20 That study found that10% of women were hospitalized duringthe year following the birth of a child andthat 14% rated themselves to be in poor or

fair health. That study also found thatwomen who delivered a low-birthweightinfant were more likely to be in poorhealth during the year following delivery.Our findings suggest that women whogive birth to a premature, low-birthweightinfant continue to be at risk for poor healthstatus through 5 years. Unlike the cohortfrom central Harlem, the women in our

sample were not all socially disadvan-taged, but in our sample, the risk of

subsequent hospitalization was increasedby economic disadvantage.

The interpretation of our results isaffected by the limitations of the study.First, all of the women had given birth to ahigh-risk infant, and the results may notbe applicable to women with full-term,uncomplicated deliveries. The yearly rateof hospitalization observed in this cohortis higher than a national estimate forwomen aged 13 through 44.21 The rate ofhospitalization in this national sample was13.1%; when hospitalizations associatedwith delivery were excluded, the nationalrate was 6.9%. National data also showthat 7.8% of women 18 through 44 ratetheir health as fair or poor.22 However,these data include relatively small percent-ages of young mothers, and, unfortu-nately, other reports do not address theirhealth status. Our cohort may differ fromthe national samples in ways that we

cannot examine.Second, the outcomes that we exam-

ined were self-reported. Although we didnot confirm hospitalizations by reviewing

American Journal of Public Health 1153

TABLE 2-Factors Associated with Hospitalization during the 5 Yearsfollowing the Birth of a Low-Birthweight, Premature Infant

AdjustedaRelative Risk 95% Cl

Subsequent pregnancy 14.97 12.70,19.10Primiparous on study enrollment 0.72 0.56, 0.93Currently employed 0.77 0.60, 0.97Currently in poor or fair health 2.03 1.55, 2.66Income <$10 000 per year 0.73 0.57, 0.97History of asthma 1.79 0.90, 3.58

Note. Cl = confidence interval.aAlso adjusted for matemal age, race, participation in the intervention, and study site.

TABLE 3-Factors Associated with Hospitalization for a Non-Pregnancy-Related Indication during the 5 Years following the Birth of aLow-Birthweight, Premature Infant

AdjustedaRelative Risk 95% Cl

Currently in poor or fair health 2.39 1.86, 3.07Subsequent pregnancy 1.29 0.99,1.67Insurance statusPrvate 1.04 0.72,1.51Medicaid 1.25 0.90,1.73

History of asthma 2.24 1.31, 3.80Currently in school 0.77 0.50,1.16History of a very-low-birthweight infant 0.82 0.62, 1.08

Note. Cl = confidence interval.aAlso adjusted for matemal age, race, participation in the intervention, and study site.

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Haas and McCormick

medical records, the health events thatcaused hospitalization were likely to havebeen accurately recalled, particularly overa 12-month period.23 Third, these womenwere participants in a specific study andmay differ from those who did notparticipate. This factor may influenceinterpretation of our study in severalways. This sample is an institutionallybased sample of women delivering atlarge, tertiary hospitals who may be athigher risk of health problems. Whileenrollment and retention rates are high,with few differences between those seenat 5 years and those not seen,115 theenrollment criteria may further affectgeneralizability. These criteria essentiallyreflect the implementation of the interven-tion, as the major reason for ineligibility isa residence outside a predetermined dis-tance from the proposed day care center.However, a small percentage of familieswere ineligible because their motherswere considered too ill to participate or

not capable of responding to an interven-tion delivered in English. Thus, althoughthe institutional base may bias the resultstoward women with health problems, asmall number with severe health oremotional problems may have been ex-cluded, and the results will not pertain towomen without some fluency in English.

Because of these limitations, manyquestions of causality and risk of ill healthfor women with an adverse birth outcomerelative to other mothers cannot beanswered. However, the substantial mor-bidity observed among women with apremature, low-birthweight infant has notpreviously been reported and, if verifiedin other studies, has several implications.Recent public policy has expanded healthcoverage to pregnant women with thegoal of ultimately improving birth out-comes. These programs, however, havenot documented improvements in mater-nal or infant health status.>7 The lack ofcontinuity of health care for women of

reproductive age24 may contribute to thesubstantial morbidity observed in thispopulation. Since public insurance pro-grams are typically limited to the prenataland immediate postpartum period, accessto health care may be particularly limitedfor postpartum women.25 This work sug-gests the need for continuous care forwomen who have experienced an adversebirth outcome. Women with other birthoutcomes were not included in this studyand need to be examined in future work.The expansion of health coverage beyondthe traditional prenatal period and bettercontinuity between obstetrical and pri-mary care providers are two interventionsthat might improve maternal health statusand, perhaps, the health status of subse-quent children. I]

AcknowledgmentsThe Infant Health and Development Programwas supported by grants from The RobertWood Johnson Foundation, the Pew CharitableTrusts, the Bureau of Maternal and ChildHealth (MCJ-360593-01-02-0), and the Na-tional Institute of Child Health and HumanDevelopment (HD 2734401A1). Dr Haas is therecipient of a Clinical Investigator Award fromthe National Institute of Child Health andHuman Development (K08-HD01029).

Members of the Infant Health and Devel-opment Program include the following: Longi-tudinal Study Office: Cecelia M. McCarton,MD (Albert Einstein College of Medicine,Bronx, NY), J. Brooks-Gunn, PhD (ColumbiaUniversity, New York, NY), and David T. Scott,PhD (Yale University School ofMedicine, NewHaven, Conn). Data Coordinating Center:James Tonascia, PhD, and Curtis L. Meinert,PhD (Johns Hopkins School of Hygiene andPublic Health, Baltimore, Md). Participatinguniversities: University of Arkansas for Medi-cal Sciences (Little Rock); Albert EinsteinCollege of Medicine (Bronx, NY), HarvardMedical School (Boston, Mass), University ofMiami School of Medicine (Miami, Fla),University of Pennsylvania School of Medicine(Philadelphia), University of Texas HealthScience Center at Dallas, University of Wash-ington School of Medicine (Seattle), and YaleUniversity School of Medicine (New Haven,Conn). Site directors: Charles R. Bauer, MD(Miami, Fla), Judy Bernbaum, MD (Pennsylva-nia), Patrick H. Casey, MD (Arkansas), CeceliaM. McCarton, MD (Einstein), Marie McCor-mick, MD (Harvard), Clifford J. Sells, MD, andForrest C. Bennett, MD (Washington), David T.Scott, PhD (Yale), and Jon E. Tyson, MD, andMark Swanson, MD (Texas). Executive Com-mittee: Cecelia M. McCarton, MD, chair(Einstein), J. Brooks-Gunn, PhD, co-chair(Columbia University), Patrick H. Casey, MD(Arkansas), David T. Scott, PhD (Yale), JamesTonascia, PhD (Johns Hopkins), Curtis L.Meinert, PhD (Johns Hopkins), and SamShapiro, special consultant to the LongitudinalStudy Office and ex-officio member of theExecutive Committee (Johns Hopkins).

1154 American Journal of Public Health

TABLE 4-Factors Associated with Poor or Fair Health 5 Years following theBirth of a Premature, Low-Birthweight Infant

AdjustedaOdds Ratio 95% Cl

Years of employmentNone ...

1 year 0.86 0.54, 1.38>1 year 0.55 0.36, 0.86

Years in poor or fair healthNone1 year 3.17 2.04,4.94>1 year 8.42 5.50,12.88

Years with an income <$10 000None ...

1 year 1.25 0.68, 2.30>1 year 3.28 1.90, 5.66

Years with Medicaid coverageNone1 year 0.79 0.43,1.45>1 year 0.26 0.15, 0.46

Years with private coverageNone ...

1 year 0.44 0.24, 0.84>1 year 0.42 0.22, 0.79

Years that child had ongoing morbidityNone ...

1 year 1.20 0.77,1.88>1 year 1.49 0.95,2.33

Subsequent number of pregnancies0 ...

1 0.63 0.35,1.15>1 0.77 0.52,1.12

History of obesity 3.30 1.44, 7.55

Note. Cl = confidence interval.aAlso adjusted for maternal age, race, participation in the intervention, and study site.

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Maternal Health after Premature Birth

We thank Arnold Epstein, MD, forhelpful comments on an earlier version of themanuscript.

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