Estimating the Number of Substance-Exposed Infants

Reports of a rising tide of illegal drug use during pregnancy are often accepted as truth. In fact, the exact prevalence rates of substance exposure during pregnancy are not known. Studies of legal and illegal substance exposure are difficult because of the sensitive nature of the behaviors involved. Traditional methods of investigation, such as asking mothers to report their own drug use, underestimate actual prevalence rates. More sensitive methods, such as blood or urine analyses, can only capture substance exposure during a narrow time frame. Who is tested is as difficult a problem as the methods that are used in the testing: a few, excellent studies have looked at a whole county or state, but, more often, studies have considered small groups of women who may not be representative of the nation at large. We reviewed 27 reports published or presented during or after 1980 and also derived our own estimates, based on National Institute on Drug Abuse data, of likely substance exposure rates for women aged 12-34. Based on the two best studies that used a single urine test to measure substance exposure, we conclude that between 2%-3% of newborns each year across the country may be cocaine-exposed, and 3%-12%, marijuana-exposed while in the womb. Studies of some smaller groups of women indicate that some places in the nation have higher exposure rates. If we consider the number of women who may have used an illegal drug at any time during their pregnancies, then interviews indicate that the exposure rates may climb to 4.5% for cocaine and 17.4% for marijuana. For comparison, cigarette and alcohol exposure occurs among 38% and 73% of all pregnancies, respectively.