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Prevalence of Drug-Exposed InfantsPatricia H. Shiono

I

n the Spring 1991 issue of The Future of Children on Drug-ExposedInfants, based on the best available evidence, it was estimated thatbetween 2% and 3% of newborns may be cocaine-exposed and between

3% and 12% may be marijuana-exposed while in the womb.1 Three newstatewide surveys and two large surveys have since been completed.26 Thesenew studies are notable because they used some of the most reliable meth-ods to assess drug exposure: They screened the mothers or newborn babysurine, blood, and/or meconium (stool); and they surveyed the popula-tion in an entire state, or large representative populations. This articleupdates the estimates of the number of substance-exposed infants, exam-ines racial group differences in illicit drug use by pregnant women, andupdates the information on the birth outcomes of women who use drugsduring pregnancy.

Patricia H. ShionPh.D., is director research and grants f

epidemiology at tCenter for the Future Children.

The Future of Children FINANCING CHILD CARE Vol. 6 No. 2 Summer/Fall 1996

REVISITING

THE ISSUES

The Prevalence of IllicitDrug Use During Pregnancy

CocaineMeasures of drug use by pregnant women inan entire state (for example, California,Ohio, Rhode Island, and South Carolina)24

continue to report much lower rates of sub-stance exposure than do studies based atselected hospitals (for example, BostonHospital).7 (See Table 1.) Rates of cocaineuse during pregnancy in the four statewide

studies ranged from a low of 0.7% in Utah toa high of 2.6% in Rhode Island. Cocaine usewas also very low at ten clinic sites in Utah(0.7%) and slightly higher in a study ofseven university hospitals across the UnitedStates (2.3%). Surveys at selected hospitalsstill have the highest reported rates ofcocaine use (46% among a selected high-

risk group in San Francisco8

and 18% inBoston7).

The data from 1984 through 1992, sug-gest that each year approximately 1% to 2%,or 35,000 to 70,000 infants, were borncocaine-exposed in the United States. Thisnew estimate is lower than that used in thisjournal in 1991 because of the relatively lowexposure rates in the recent statewide stud-ies. It is unclear if the lower reported rates ofdrug use from the recent statewide surveysare the result of overall reductions in the use

of cocaine over time, the result of the selec-tion of more representative samples ofwomen, or a combination of both.

MarijuanaRates of marijuana use during pregnancyare higher than rates of cocaine use dur-ing pregnancy. Marijuana use in the four


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160 THE FUTURE OF CHILDREN SUMMER/FALL 1996160

Study/Location, DrugsEndnote Number,aYear(s),

and Screening Method Cocaine Marijuana Opiates Other Cigarettes Alcohol

Boston City Hospital7 18.0 27.0 3.9 3.0 41.0b 59.0b

1984 through 1987Mothers urine duringpregnancy and after delivery

Seven University Hospitals6 2.3 11.0 35.0b 34.1b

1984 through 1989Mothers blood duringpregnancy and maternalinterviews

Pinellas County, Florida1 3.4 11.9 0.31989Mothers urine duringpregnancy

Rhode Island1 2.6 3.0 1.7 0.2c 1.0d

1989Mothers urine at delivery

National Institute on DrugAbuse Survey1 4.5 17.4 1.1 to 2.6 37.6 73.01990Interviews with nonpregnantwomen

Ohio5 1.41990Babys urine after birth

South Carolina2 0.8 2.5 2.2 1.9

1990 through 1991Mothers urine at delivery andinfant meconium

California4 1.1 1.9 1.5 0.7c 8.8b 6.7

1992Mothers urine at delivery

Ten Clinics in Utah5 0.7 3.1 1.6 0.1c 5.21992Mothers urine duringpregnancy

a See the related endnote following this article for the complete citation of a publication in which the relevant study is describedand/or discussed.

b Information based on an interview with the mother.

c The other drugs identified were amphetamines.

d Information based on infant urine screening at birth.

Table 1

Percentage of Mothers Using Drugs During Pregnancy


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161REVISITING THE ISSUES: Prevalence of Drug-Exposed Infants

statewide studies ranged from a low of 1.9%(in California) to a high of 3.0% (in RhodeIsland). Like cocaine, much higher rates ofmarijuana use were detected at specific hos-pitals (27% in Boston, 12% in PinellasCounty, Florida, and 11% in seven university-based clinics). The data from 1984 through

1992 suggest that each year approximately2% to 3%, or 70,000 to 105,000 infants, wereborn marijuana-exposed in the UnitedStates. Recent data based on the NationalHousehold Survey on Drug Abuse9 suggestthat marijuana use may have peaked in theearly 1980s and has been declining since.However, data from individual clinic sitesis conflicting. A New York City study showedan increase in marijuana use between 1988and 1992,9 and a study of seven university-based clinics from 1984 through 1989showed a significant decrease in marijuana

use starting in 1988.6

Racial Group Differences inDrug Use During PregnancyThe recent completion of large statewidestudies provide clear evidence of large racialgroup differences in illicit drug use by preg-nant women. These statewide studies allused scientific sampling methods to obtain arepresentative sample of pregnant womenin the state. Among the four statewide stud-

ies, rates of cocaine use during pregnancywere between 4 and 26 times higher amongAfrican-American women than among whitewomen. An exception to this was the seven-university clinic study, where there were noracial group differences in cocaine use.Among the four statewide studies, whitewomen were approximately two to threetimes more likely to use marijuana duringpregnancy than African-American women.The Rhode Island and California surveysshowed little or no difference in marijuanause by race. Asian and Hispanic women in

California had extremely low rates of illicitdrug use during pregnancy.

Birth Outcomes ofSubstance-Exposed InfantsIn contrast to the number of excellent stud-ies that provide good estimates of the num-ber of women who use drugs during preg-nancy, there are few studies that examine thepregnancy outcomes of these women. Initialreports have tended to show very high corre-

lations between adverse pregnancy outcomessuch as low birth weight and preterm birth.10

However, most studies linking drug use andpregnancy outcomes have been inconclusivebecause they were confined to very small orhighly selected subgroups of women, reliedon self-reported information about drug

use, or did not control for important con-founding factors.6 These types of shortcom-ings in study design would all tend to biasthe study results toward finding positive asso-ciations between drug use and birth out-comes, even when positive associations trulydid not exist. In addition, publication bias,where scientists and publishers are morelikely to submit and publish studies with pos-itive findings, may also have played a role inthe dissemination of information about illic-it drug use and pregnancy outcome.

New evidence from a large multicenterstudy showed no association betweencocaine or marijuana use during pregnancyand low birth weight or preterm births.6 Thisstudy was one of the first to use unbiasedmethods to measure both drug exposureand pregnancy outcomes. Informationabout drug use was obtained by blood serum

screening and personal interviews at sevenuniversity-based clinics across the UnitedStates. Results indicated that cocaine andmarijuana use in these seven clinics was rareand was not related to increased rates ofinfant low birth weight or preterm birth.Therefore, the elimination of cocaine ormarijuana use in this population of women

would have little or no measurable impacton birth outcomes.

The women at these seven clinics were aselected sample of women who came in forprenatal care, which makes them a popula-tion much less likely to use drugs. There isgood evidence from the California surveythat women who receive no prenatal carehave the highest rates of drug use.4 InCalifornia, cocaine was used by 11.5% ofpregnant women who received no prenatal

The data from 1984 through 1992 suggestthat each year approximately 2% to 3%,

or 70,000 to 105,000 infants, were bornmarijuana-exposed in the United States.


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162 THE FUTURE OF CHILDREN SUMMER/FALL 1996

care, amphetamines by 7.0%, and marijuanaby 5.7%. However, only 2.4% of all thewomen in California did not obtain any pre-natal care. Even though illicit drug use isrelatively common among women whoobtain no prenatal care, the number ofwomen who obtain no prenatal care is rela-

tively small and, therefore, will have littleimpact on overall rates of drug use or birthoutcomes.

Although tens of thousands of womenuse illicit drugs during pregnancy, mostwomen use drugs only occasionally. Basedupon data from the statewide surveys, con-sistent abuse of illicit drugs appears to berelatively uncommon among pregnantwomen in the United States in general. Theoccasional use of drugs during pregnancy,which is typified in the seven-clinic study,

appears to have little or no measurable effect

on birth outcomes such as low birth weightor prematurity.6 However, there is clearevidence that regular use or the abuse of

cocaine has the potential to cause harm tothe fetus.10 Very high serum concentra-tions of cocaine and marijuana metaboliteswere associated with low birth weight andpreterm birth.6

ConclusionsFrom the accumulated data, it is clear thatthere was no widespread nationwide epi-demic of cocaine use among pregnantwomen in the United States during the mid-1980s to early 1990s. Based on data from1984 through 1992, each year approxi-

mately 1% to 2%, or 35,000 to 70,000infants, were born cocaine-exposed. How-ever, rates of cocaine drug use at particularcities or hospitals appear to be very high.Recent data based on general populationsurveys suggest that cocaine use may havepeaked in the late 1980s and decreased inthe early 1990s.

Marijuana is the most commonly usedillicit drug in the United States.11As is true ofcocaine, there is no evidence of a wide-

spread nationwide epidemic of marijuanause during pregnancy; however, there areseveral hospitals across the United Stateswith very high rates of marijuana use amongpregnant women. As many as 2% to 3%, or70,000 to 105,000 infants, each year wereborn marijuana-exposed. Recent data based

on general population surveys suggest thatmarijuana use may have peaked in the earlyto mid-1980s and has been declining sincethe late 1980s.

Universal screening for drug use amongpregnant women is not a productive methodto identify drug users. The low prevalence ofillicit drug use nationally makes widespreadscreening very inefficient. Moreover, accu-rate information about drug use duringpregnancy in any population is virtuallyimpossible to obtain. Surveys often underes-

timate drug use during pregnancy. Drugtests of urine or blood often miss womenwho use illicit drugs once or twice duringpregnancy. Women are also reluctant toreport illicit drug use during pregnancy tohealth care providers. Moreover, surveys ofdrug use during pregnancy exclude womenwho do not come in for prenatal care.Future surveys and studies may need to relyon testing of maternal hair which is ableto provide information about the history ofdrug use during the entire pregnancy.12

The discovery of large racial group dif-ferences in drug use by pregnant women inCalifornia led the studys authors to recom-mend that communities with large African-American populations be targeted for exten-sive clinical and educational interventions.4

They suggested several strategies to reducethe number of women who might use drugsduring pregnancy in the future.4 Strategiesincluded prenatal drug counseling and resi-dential treatment programs for pregnantwomen and educational campaigns for

African-American adolescents. It was alsonoted that keeping young African-Americanwomen from starting to use drugs would bean especially promising strategy becauseAfrican-American women appear to startdrug use at a much later age than adoles-cents from other racial groups.

A disturbing finding in the statewide sur-veys of drug use is that women who receiveno prenatal care, while representing only2.4% of all pregnant women, are the ones

Cigarette smoking is the single largestmodifiable cause of low birth weight andinfant mortality.


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163REVISITING THE ISSUES: Prevalence of Drug-Exposed Infants

most likely to use illicit drugs during preg-nancy. Drug-abusing women as a groupwould benefit greatly from prenatal care if itincluded appropriate drug counseling anddrug cessation therapy.

All of the media attention surrounding

the use of cocaine and crack should notdivert public attention from the largestknown risk to the health of unborn babiescigarette smoking. Virtually all studies showthat tobacco is clearly the most commonly

abused drug during pregnancy. Because ofits high rate of use and the large impact ithas on the fetus, cigarette smoking is the sin-gle largest modifiable cause of low birthweight and infant mortality.13 Cigarettesmoking causes up to 20% of all low birthweight infants.13Women who quit smoking

during pregnancy significantly reduce thechances that their baby will be born lowbirth weight. A key element of all prenatalcare, therefore, should be access to smokingcessation programs.

1. Gomby, D.S., and Shiono, P.H. Estimating the number of substance-exposed infants. TheFuture of Children(Spring 1991) 1,1:1725.

2. State Council on Maternal Infant and Child Health. 1991 South Carolina prevalence studyof drug use among women giving birth. Office of the Governor, South Carolina, 1991.

3. Moser, J.M., Jones, V.H., and Kuthy, M.L. Use of cocaine during the immediate prepartumperiod by childbearing women in Ohio. American Journal of Preventive Medicine(1993)

9:8591.

4. Vega, W.A., Kolody, B., Hwang, J., and Noble, A. Prevalence and magnitude of perinatalsubstance exposures in California. New England Journal of Medicine(1993) 329:85054.

5. Buchi, K.F., and Varner, M.W. Prenatal substance use in a western urban community.Western Journal of Medicine(1994) 161:48386.

6. Shiono, P.H., Klebanoff, M.A., Nugent, R.A., et. al. The impact of cocaine and marijuanause on low birth weight and preterm birth: A multicenter study. American Journal ofObstetrics and Gynecology(1995) 172:1927.

7. Zuckerman, B., Frank, D.A., Hingson, R., et al. Effects of maternal marijuana and cocaineuse on fetal growth. New England Journal of Medicine(1989) 320:76268.

8. Osterloh, J.D., and Lee, B.L. Urine drug screening in mothers and newborns. AmericanJournal of Diseases in Children(1989) 143:79193.

9. McCalla, S., Feldman, J., Webbeh, H., et. al. Changes in perinatal cocaine use in an inner-city hospital, 19881992. American Journal of Public Health(1995) 85:169597.

10. Holzman, C., and Paneth, N. Maternal cocaine use during pregnancy and perinatal out-comes.Epidemiologic Reviews(1994) 16:31534.

11. Substance Abuse and Mental Health Services Administration, Rockville, MD. PreliminaryEstimates from the 1994 National household survey on drug abuse. U.S. Department of Healthand Human Services, Advance Report No. 10, September 1995.

12. Ostrea, E.M., and Welch, R.A. Detection of prenatal drug exposure in the pregnantwoman and her newborn infant. Clinics in Perinatology(1991) 18:62945.

13. Shiono, P.H., and Behrman, R.E. Low birth weight: Analysis and recommendations. TheFuture of Children(Spring 1995) 5,1:48.

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