Illicit drug use and adverse birth outcomes: is it drugs or context?

Prenatal drug use is commonly associated with adverse birth outcomes, yet no studies have controlled for a comprehensive set of associated social, psychosocial, behavioral, and biomedical risk factors. We examined the degree to which adverse birth outcomes associated with drug use are due to the drugs versus surrounding factors. Data are from a clinical sample of low-income women who delivered at Johns Hopkins Hospital between 1995 and 1996 (n = 808). Use of marijuana, cocaine, and opiates was determined by self-report, medical record, and urine toxicology screens at delivery. Information on various social, psychosocial, behavioral, and biomedical risk factors was gathered from a postpartum interview or the medical record. Multivariable regression models of birth outcomes (continuous birth weight and low birth weight ([LBW] < 2,500 g)) were used to assess the effect of drug use independent of associated factors. In unadjusted results, all types of drug use were related to birth weight decrements and increased odds of LBW. However, only the effect of cocaine on continuous birth weight remained significant after adjusting for all associated factors (-142 g, p = 0.05). No drug was significantly related to LBW in fully adjusted models. About 70% of the unadjusted effect of cocaine use on continuous birth weight was explained by surrounding psychosocial and behavioral factors, particularly smoking and stress. Most of the unadjusted effects of opiate use were explained by smoking and lack of early prenatal care. Thus, prevention efforts that aim to improve newborn health must also address the surrounding context in which drug use frequently occurs.