EFFECTS OF PRENATAL DRUG EXPOSURE
The effects of prenatal drug exposure cannot be isolated from many other factors affecting developmental outcome. Furthermore, accurate history of all exposures during pregnancy is difficult if not impossible to ascertain. For example, in an anonymous prevalence study in an inner-city Maryland teaching hospital, 18% of mothers admitted drug use, but 48% of infants had symptoms indicating recent drug exposures. Half had evidence of exposure to more than one drug. In a similar survey, 38% of women reported cocaine use during pregnancy, but 60% had positive results by hair sample analysis. Multiple exposures are also common. For example, in a survey of 65 Swedish mothers evaluated for amphetamine use during pregnancy, 30% also used heroin, 80% abused alcohol, and 80% smoked. Ninety-four percent of drug-abusing mothers in Holland used multiple drugs (methadone, heroin, cocaine, amphetamines, tranquilizers), and all smoked. Regardless of the primary drug of choice, tobacco and alcohol are frequently combined. Combinations of drugs may be more devastating than single agents for the developing fetus. Tobacco smoke and cocaine combine synergistically to increase the risks of prematurity and intrauterine growth retardation. Cocaine and alcohol together form cocaethylene, which is more neurotoxic than cocaine alone.
Thus studies that purport to show the effect of a single type of drug exposure on the fetus may be misleading. Accurate information on the type, potency, amount, frequency, and duration of drug use during pregnancy is essentially unavailable outside of laboratory animal settings.