Journal Issue: Drug-Exposed Infants Volume 1 Number 1 Spring 1991
Evidence from Previous Studies
All the preceding caveats are not to suggest that we have nothing at all to go on. We reviewed 27 studies, all published or presented during or after 1980, to estimate prevalence rates of illegal drug exposure among pregnant women to cocaine, marijuana, opiates (heroin and/or morphine), and other illegal drugs, such as stimulants, hallucinogens, and tranquilizers. For comparison, we also describe rates of alcohol and cigarette use during pregnancy, as reported by other researchers. In addition, we calculated our own estimates of the prevalence of substance use among pregnant women, based upon data from the National Institute on Drug Abuse (NIDA) 1990 National Household Survey on Drug Abuse.Sources of Information
The best sources of information about substance exposure during pregnancy are two population-based studies of all pregnant women in Rhode Island5 and Pinellas County, Florida,6 during 1989, and the continuing work of Dr. Barry Zuckerman and his colleagues at Boston City Hospital.2,7
The Rhode Island study involved the testing of urine specimens of 65% of all pregnant women who delivered at Rhode Island hospitals during October and November of 1989. Urine was tested for metabolites of cocaine, opiates, amphetamines, and marijuana.
The Pinellas County, Florida, study involved urine tests of all pregnant women who enrolled for prenatal care in the first 6 months of 1989 at any of the 5 public health clinics and 12 of 20 private obstetrical practices in the county. The urine was tested for alcohol, opiates, cocaine, and marijuana.
In both these studies, women's urine was tested once, either at delivery or at first prenatal visit. In contrast, in the studies conducted at Boston City Hospital between 1984 and 1987, women's urine was tested for marijuana and cocaine twice, both at their first prenatal visit and after delivery. In addition, women were interviewed at each of those points in time and asked about their use of alcohol, cigarettes, heroin, amphetamines, and phencyclidine (PCP).
As mentioned above, we utilized the NIDA 1990 National Household Survey on Drug Abuse8 to calculate our own estimates of the prevalence of substance abuse among pregnant women. Periodically, NIDA interviews individuals in households across the nation about their use of a variety of legal and illegal substances at various points during their lives. Results are not reported separately for pregnant women, but we estimated the prevalence of legal and illegal substance use during pregnancy by multiplying the substance exposure rates within the previous year by the 1987 birth rates for three age groups (ages 12–17, 18–25, and 26–34). In 1987 about 92% of all births occurred among these age groups.9 Figures 1 and 2 illustrate the substance exposure rates based on NIDA estimates for all women, and the birth rates of all women by age group. Taken together, the figures indicate that the age groups with the highest birth rates are also the age groups most likely to use legal and illegal drugs.
Results of the Rhode Island, Pinellas County, and Boston City Hospital studies, which are the most comprehensive and carefully conducted of those we reviewed, are discussed below, along with results of other relevant hospital-based studies and our own estimates of legal and illegal substance use prevalence.Cocaine
In Rhode Island cocaine was detected in 2.6% of the women tested. In Pinellas County 3.4% of the women tested positive for cocaine. In both studies more non-White than White women used cocaine.
The women in the Boston City Hospital study had the highest rates of cocaine use: 18%.2 Remember, however, that these results reflect both maternal self-reports and urine screenings at two different times.
Other studies of women at particular hospitals produce prevalence rates ranging from 1% to 36%. Rates vary, depending on what form of screening is used (e.g., self-reports,10-12 urine tests of mother,5,6,12,13 maternal self-reports plus urine tests of mother or child,2,7,14-16 urine tests of baby,12,17 stools of the newborn),18 and which women were screened. The highest rate reported (36%), for example, was found among women who had not received prenatal care but who arrived at the hospital only to deliver their babies.14
Two other hospital surveys found similar ranges. The General Accounting Office reviewed medical charts of mothers and infants in 10 hospitals in 5 cities (Boston, Chicago, Los Angeles, New York, and San Antonio) and found rates of cocaine use that ranged from 0.3%–11.6%.3 In a survey of 40 hospitals, rates of cocaine exposure among pregnant women or their babies in the 36 hospitals that responded to the survey were estimated to be from 0.4% to 27%, based on discharge diagnosis of the mother or infant.12 Authors of both surveys attributed the differences to the hospitals' varied screening policies. As mentioned above, however, it is possible that the hospitals that instituted stringent screening procedures (and found higher rates) were the very hospitals with the higher rates to begin with.
Based upon NIDA's 1990 Household Survey, we estimate that 4.5% of pregnant women between the ages of 12 and 34 may have used cocaine during pregnancy.Marijuana
In the Rhode Island study, 3% tested positive for marijuana. The Pinellas County study yielded a rate of 11.9%. In both these studies, rates for marijuana use were higher among White than among non-White women. Zuckerman and his colleagues at Boston City Hospital found a rate of 27%.2
Two other hospital-based studies, one in Philadelphia13 and one in Detroit,18 found rates of exposure of 4.0% and 12.1%, respectively.
Our estimate, based on NIDA's Household Survey, indicates that 17.4% of pregnant 12- to 34-year-olds may have been exposed to marijuana sometime during their pregnancies.Opiates
Rates of opiate exposure (heroin, opium, and/or morphine) range from 0.3% in the Pinellas County study, to 1.7% in the Rhode Island study, to 4.0% in Boston City Hospital.7 Three other hospital-based studies found rates ranging from 0.2%, when mothers self-reported, to 23.3% when the stools of a selected group of infants were tested.13,18,19Other Drugs
A few studies have measured exposure to other drugs. The Rhode Island study found only one woman who tested positive for amphetamines (a rate of 0.2%). In the survey of 36 hospitals mentioned above, the author reports that 3% of the mothers entering prenatal care at Parkland Memorial Hospital in Dallas said they had used amphetamines during pregnancy.12 Between 1984 and 1986, Boston City Hospital reported a 3.0% rate for all illegal drugs other than cocaine, marijuana, and opiates.
We estimate, based upon NIDA's 1990 Household Survey, that 1.2% of pregnant 12- to 34-year-olds may have used hallucinogens; 1.1%, sedatives; and 2.6%, stimulants during their pregnancies.Alcohol
Fifty-nine percent of the women in the Boston City Hospital study acknowledged that they had drunk alcohol during their pregnancies.7 In contrast, data from the Pinellas County study, in which women's urine was tested, indicated only a 1% rate, not too surprising given that urine tests are sensitive to alcohol use only within the past few hours.
Estimates of abusive drinking among women of reproductive age are 3%–4%.20 The incidence of fetal alcohol syndrome (FAS), a particular collection of birth defects that sometimes accompanies heavy alcohol use during pregnancy, is approximately 1.9 births per thousand (0.19%).12
Based on data from NIDA's 1990 Household Survey, we estimate that as many as 73% of pregnant 12- to 34-year-olds may have drunk alcohol sometime during their pregnancies.Cigarettes
Forty-one percent of the women in the Boston City Hospital study smoked during their pregnancies.7 In the United States in 1980, 43% of married women with less than 12 years of education, 28% of those with 12 years, and 11% of those with greater than 16 years smoked during pregnancy.22 State of Missouri vital records for 1988 indicate that 26.9% of pregnant women in that state smoked during their pregnancies.23
Our estimates, based upon NIDA's 1990 Household Survey, indicate that 37.6% of pregnant 12- to 34-year-olds may have smoked cigarettes during pregnancy.Use of Multiple Substances
Several studies indicate that many pregnant women who use one substance also use one or more other drugs, alcohol, or cigarettes.2,7,13,18,19,24,25 In a study of infants delivered during 1988 and 1989 at a tertiary perinatal center in Detroit, for example, 20.8% of the infants tested positive for cocaine, but only 10% showed no signs of any other substances.18 Similarly, while 23.3% tested positive for opiates (heroin or morphine), only 13.3% showed no signs of any other drugs. In the same sample, 11.1% of the babies tested positive for more than two substances.26