Neurobehavioral sequelae of fetal cocaine exposure

Abstract

The number of infants born to cocaine-using mothers has continued to rise during the past 5 years. Maternal cocaine use during pregnancy is associated with medical and life-style characteristics detrimental to fetal and infant development. Cocaine exposure has been independently linked to growth retardation and impaired fetal oxygenation even when polydrug use and other confounding factors are considered. Neurologic and neurobehavioral abnormalities noted in the immediate neonatal period have also been associated with fetal cocaine exposure. The direct and indirect toxic effects of cocaine, per se, have not yet been independently linked to specific behavioral outcomes because of small sample sizes, confounding factors, and lack of long-term follow-up. The impoverished environments and increased risk for out-of-family placement of cocaine-exposed infants are known independent correlates of negative developmental outcomes. Poor maternal nutrition, lack of prenatal care, and other health and life-style factors related to maternal cocaine use during pregnancy also appear to be factors mediating the developmental problems of cocaine-exposed infants. The cocaine-using mother often uses other drugs, particularly alcohol, independently known to be linked to growth and behavioral impairments similar to those proposed for cocaine-exposed infants. Accounting for these multiple confounding variables in studies of the specific effects of cocaine on neurobehavioral outcome may be scientifically appropriate, but in clinical practice these factors cannot be "isolated," and their statistical consideration in studies does not diminish clinical risk. Finally, currently available studies of behavioral outcome have restricted their samples to term infants. It is possible that preterm infants may be less affected by prenatal cocaine exposure because of decreased exposure. However, because epidemiologic studies suggest that prematurity is a sequelae of maternal cocaine use, restriction of samples to term or appropriately sized infants may underestimate the spectrum of morbidity associated with cocaine exposure. We believe that maternal cocaine use during pregnancy is a "marker" variable for early impairments in infant growth and behavioral functioning that have long-term implications for later developmental outcome, especially for learning disabilities and behavioral disorders. Critically assessing the independent contribution of cocaine to negative developmental outcome and determining whether early neonatal abnormalities are permanent or modifiable may allow clinical intervention and improved social policy. Assessing the independent effects of cocaine on child developmental outcome will require carefully designed, long-term, longitudinal, population-based studies with samples large enough to allow multivariate data analyses and statistical control of confounding medical and social variables.