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Pregnancy-Related Substance Use in the United States During 1996–1998

Ebrahim, Shahul H. MD, PhD; Gfroerer, Joseph

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Illicit drug use is the ninth leading contributing cause of death in the United States.1 The public health concern about substance use during pregnancy is reflected in the statement by the US Senate Committee on Appropriations in 1991, which called for monitoring its trends and adverse effects.2 Although the evidence about the adverse effects of prenatal illicit drug use on pregnancy and childhood have been inconsistent, with some studies showing an association between illicit drug use and adverse maternal and child health outcomes and other studies showing no such association,3–7 prenatal illicit drug use is a topic that has evoked multifaceted legal and political controversies.7,8 The role of illicit drug use in the transmission of human immunodeficiency virus (HIV) remains most clearly appreciated. Clearly, illicit drug use is associated with increased morbidity and mortality and also predisposes women who use illicit drugs to other risk factors that are harmful to the women and their pregnancies including violence and transmission of HIV, hepatitis B and hepatitis C viruses, and other sexually transmitted infections.1,9–12

Baseline data on the burden of prenatal substance use is needed to monitor progress towards the Year 2010 national objective on substance abuse reduction by pregnant women (ie, to increase abstinence from illicit drugs during pregnancy to 100%).13 Surveillance of illicit drug use is difficult. Urine toxicology screens are expensive and are sensitive only in a specific time frame. Use of hair for assessment of drug use is limited by the fact that coarse black hair incorporates more of the drug than brown or blond hair, necessitating the need for differential scaling by hair color. Both the hospital discharge data and birth certificate-based data on substance use are subject to bias in data collection and reporting. Therefore, self-report surveys remain a rational choice for surveillance of prenatal drug exposure. From 1994 on, the National Household Survey on Drug Abuse included questions on pregnancy status for childbearing-aged women.14 The National Household Survey on Drug Abuse is the only national survey that allows assessment of substance use behaviors by trimester of pregnancy.

In this study, we used the National Household Survey on Drug Abuse data to estimate the prevalence of illicit drug use and pregnancy-related abstinence from illicit drug use and its correlates among women of childbearing age in the United States from 1996 through 1998. Because illicit drug use is often associated with use of other substances, we included data on other substances such as tobacco and alcohol.


The National Household Survey on Drug Abuse,14 which is conducted annually by the Substance Abuse and Mental Health Services Administration, is intended to monitor trends in the use of illicit drugs, alcohol, and tobacco and the demographic correlates of their use. This survey uses a household-based probability sample of the civilian population aged 12 and older, and is designed to provide estimates representative of the US population. The survey covers residents of households, noninstitutionalized group shelters (eg, shelters, rooming houses, dormitories), and civilians living on military bases. The sample design incorporates over-sampling of blacks, Hispanics, and young people to improve the accuracy of estimates for those populations. Survey interviews are conducted anonymously in respondents' homes and average an hour to complete. To ensure privacy for sensitive questions, some of the modules including those on substance use are self-administered.

During the study period, response rates were 93% for household screening and 79% for completing interviews. The questions on illicit drug use, alcohol, and cigarette use asked in this survey have been published.14 In this survey, illicit drug use is defined as at least one time use of marijuana/hashish, cocaine (including crack), inhalants, hallucinogens (including PCP and LSD), heroin, or any prescription-type psychotherapeutic drugs used nonmedically. In this paper, substance use refers to use of any of the illicit drugs, alcohol, or cigarettes. In this survey, current substance use is defined as use in the 30 days before the survey interview. Therefore, women who quit use of a substance before the 30-day time frame would not be counted among current users of that substance, but they would be counted among lifetime users of that substance. The question on pregnancy status is asked after other questions have been asked. Those who provide an affirmative response to the question “Are you currently pregnant?” are asked “How many months pregnant are you?”

We obtained the percentage of women aged 18–44 years who reported lifetime and current use of illicit drugs, alcohol, or cigarettes stratified by pregnancy status. We estimated the pregnancy-related abstinence rate of substance use indirectly using a previously described method.15,16 Briefly, first we obtained the prevalence rate ratio of substance use between pregnant and nonpregnant women (prevalence rate ratio = % in pregnant women ÷ % in nonpregnant women).15,16 We converted the prevalence rate ratio to pregnancy- related abstinence rate using the formula (1 – prevalence rate ratio) × 100.15,16 In the absence of each woman's substance use before and after planning or recognizing a pregnancy, the prevalence rate ratio provides an indirect measure of the magnitude of the continuation of substance use after recognition of pregnancy. Because lifetime use of substances is generally similar among pregnant and nonpregnant women,15,16 prevalence rates among nonpregnant women may reflect prepregnancy rates. We also estimated the relative decline in substance use during successive trimesters. In this ecologic assessment, we assumed that concerns about harm to the pregnancy was the primary reason for changes in the prevalence rate of drug use among pregnant women during pregnancy, and that some women may relapse postpartum. Therefore, we also measured the net pregnancy-related abstinence rate from substance use at postpartum using information on prevalence rates of substance use among women with children under 2 years of age. We assumed that women with young children who used substances were also using drugs before pregnancy.

Because of sample size limitations for pregnant women, for stratified analysis by sociodemographics (age, race, education, marital status, and employment), we aggregated data from all years. National prevalence of pregnancy-related cigarette and alcohol use stratified by sociodemographics have been published,15,16 and they are not included in this analysis. All estimates make use of weighting factors to compensate for the effects of nonresponse and unequal selection probabilities. The complex sampling procedures used in the surveys require the use of the software for survey data analysis (SUDAAN; Research Triangle Institute, Research Triangle Park, NC) to obtain valid estimates of standard errors. A P value <0.05 was considered statistically significant in all analyses.


Of the 22,634 female respondents aged 18–44 years who responded to the National Household Survey on Drug Abuse from 1996 through 1998, we excluded 331 for whom data were incomplete for the pregnancy question. Of the remaining 22,303 women, 1249 reported that they were pregnant (298 in first trimester, 494 in second trimester, 457 in third trimester). Overall, 3978 women had children below 2 years of age. Pregnant women were more likely to be younger and married than their nonpregnant counterparts (Table 1).

Table 1
Table 1:
Demographics of Survey Respondents and Prevalence of Illicit Drug Use and Abstinence Among Women Aged 18–44 Years, United States, 1996–1998

Of the women surveyed during 1996 through 1998, nearly half reported using illicit drugs once in their lifetime (Table 2), and the difference by pregnancy status was not statistically significant (annual average rate: 44.6% pregnant, 46.2% nonpregnant). Similarly, there was no statistically significant difference between pregnant and nonpregnant women in the prevalence of lifetime cigarette or alcohol use.

Table 2
Table 2:
Pregnancy-Related Substance Use and Abstinence Rates, United States, 1996–1998

From 1996 through 1998, the annual average percentage of women aged 18–44 years who reported current use of illicit drugs, alcohol, or tobacco did not vary significantly (data not shown). Among those who reported illicit drug use (3-year average: 2.8% pregnant, 6.4% nonpregnant) (Table 2), more than half of pregnant women (54%) and two-thirds of nonpregnant women (65%) also used alcohol and cigarettes. Based on these prevalence rates and the number of pregnancies in 1998 in the United States, we estimated that during the first trimester, 202,000 pregnancies were exposed to illicit drugs, 1,203,000 pregnancies were exposed to cigarettes, and 823,000 pregnancies were exposed to alcohol.

Of all drug-using women, the relative proportion of women who abstained from illicit drug use after recognizing that they were pregnant increased from about one-fourth during the first trimester (or three-fourth continued illicit drug use) to 93% (or 7% continued illicit drug use) during the third trimester of pregnancy (Figure 1). However, because of large postpregnancy relapse rates, the net pregnancy-related reduction in illicit drug use at postpartum was much smaller (24%) (Figure 1). Postpregnancy relapse rate of smoking among cigarette smokers appear to be smaller than those among alcohol or illicit drug users, but cigarette users also had the smallest pregnancy-related abstinence rate than alcohol users or illicit drug users (Figure 1). The net pregnancy-related reduction was similar for cigarette use (16%) and for alcohol use (16%).

Figure 1
Figure 1:
Relative proportion of substance-using women who abstained during and after pregnancy.Ebrahim. Illicit Drug Use in Pregnancy. Obstet Gynecol 2003.

Marijuana was the most common type of illicit drug used by women aged 18–44 years accounting for three-fourths of all illicit drug use (Table 2). Cocaine accounted for one-tenth of all illicit drug use. The variation in illicit drug use by sociodemographics was generally similar among pregnant and nonpregnant women (Table 1). The percentage of women who reported illicit drug use declined with increasing age. The prevalence of illicit drug use was the highest among women who were aged 18–30 years, or unmarried, and pregnant women who had less than a high school education.


We found that, during 1996–1998, about one of 14 US women of childbearing age reported using illicit drugs in the past month, and only one-fourth of them had abstained from illicit drug use during the first trimester of pregnancy. Although nearly all women who reported illicit drug use abstained by the third trimester of their pregnancy, because of postpregnancy relapse of illicit drug use, the net pregnancy-related abstinence rate of substance use was only 24%. Marijuana was the most commonly used illicit drug. Of those who used illicit drugs, more than half of pregnant and two-thirds of nonpregnant women also used alcohol and cigarettes. Our data on demographic characteristics of women who use illicit drugs and on prevalence of alcohol and cigarette use are in agreement with previous reports.15–17 Self-reported data on pregnancy and substance use rates are likely to provide lower bound of the actual prevalence rates. Furthermore, some substance users who may be homeless, institutionalized, or living in drug treatment services are not surveyed by the National Household Survey on Drug Abuse. Despite such limitations, the National Household Survey on Drug Abuse provides a sense of the relative national burden of substance use during pregnancy including by trimester of pregnancy.

The in utero effects of some substances (“light drugs”) on fetal development and the effect of maternal use of such drugs postnatally on child development may be small when compared with the effects of “heavy drugs,” such as cocaine. Maternal cocaine use is associated with adverse maternal (abruptio placentae, preeclampsia, spontaneous abortions) and fetal effects (intrauterine growth retardation, congenital malformations, cardiovascular, and behavioral effects), which may be correlated with use of other substances and quality of the social environment.2–4,18 Neonatal hospital costs for the care of cocaine-exposed infants have been estimated to be $5200 more than that for unexposed infants.18 The costs of infants remaining in the nursery while awaiting home and social evaluation for foster care placement increased this difference by more than $3500.18 Replication is needed to evaluate the reported association of in utero marijuana exposure with reduced birth weight, behavioral, and developmental effects during the first few months after birth, and higher prevalence of childhood cancers.19 Irrespective of the inconsistency in evidence of a biological association between in utero exposure to illicit drugs and adverse maternal and fetal outcomes, the effects of postpregnancy illicit drug use by women and illicit drug use behaviors of partners of drug-using women on child development, and the impact of drug use on the women themselves are often far removed from discussions that focus solely on the biological effects of illicit drug use on children. Pregnancy-or childbirth-related contact of women with the health care system give health care providers a unique opportunity to access women who use substances and possibly their partners to facilitate substance abuse treatment, the benefits of which extend to their infants and future pregnancies. Among women who seek care, a combination of routine detailed substance abuse history and toxicology screens carried out in a nonhostile environment would identify more illicit drug-using women who would not be detected by passive methods. Finding alternatives to complete abstinence from illicit drugs might well reduce harm to mother and fetus. The number of drug-exposed pregnancies may also be reduced through voluntary contraception until abstinence from substance use is achieved.

Most women who use illicit drugs, especially those who are users of “heavy drugs” or frequent users, are likely to be those who do not seek prenatal care or delay prenatal care,17,20 and prenatal illicit drug abuse may be the most frequently missed diagnosis in all of the obstetric medicine. Further, the current legal, social, and welfare policies on prenatal illicit drug use may impede constructive exploration of the full range of social and therapeutic options.7,8,21 Given these difficulties in prenatal diagnosis and treatment of illicit drug use, interventions among women of childbearing age who are at risk for substance use would be most useful. Women who are most likely to use drug treatment services are also those who have the most severe substance abuse problems.20 However, opportunities for treatment and other services are limited; only about one-third of women in need of drug abuse services receive professional treatment for their problems.21,22 Among all substance abuse treatment facilities in 1998, one in 16 provided on-site family planning services, one in 15 facilities offered prenatal care services, and one-third of facilities offered HIV testing.21,22

One of five Medicaid hospital days, or 4 million days, were spent on substance abuse-related care in 1991 at a cost of $8 billion.11 Effective treatment and intervention options for drug addiction are available.23,24 These are powerful arguments for investing in drug abuse prevention and care for affected individuals. Ensuring adequate insurance coverage for substance abuse treatment and relapse prevention including in publicly funded programs will be crucial to decreasing the public health burden from substance abuse. Integrated efforts among programs focusing on teenage pregnancy, HIV, and sexually transmitted infections and partnerships among public health officials, communities, police, and criminal justice departments will be key to the long-term reduction of substance-exposed pregnancies. Clearly, substance-exposed pregnancies can be reduced by preventing the uptake of substance use by young people.


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© 2003 The American College of Obstetricians and Gynecologists