To determine the effect of first trimester cocaine use on pregnancy outcome we conducted a prospective cohort study of 30 women admitting to social cocaine use (SCU) during early pregnancy, 20 users of cannabis during the first trimester and 30 matched recreational drug-free control subjects. The groups were of similar age, marital status, and obstetric history and were predominantly white. They were of similar socioeconomic status (SES), however the spouses of the cocaine users were of significantly lower SES than those of both control groups (p less than 0.005). The number of years of education of the cocaine users and the fathers of the SCU-exposed fetuses was significantly lower than that of the recreational drug-free control subjects (p = 0.004), however, female IQ was similar among the three groups (109.1 +/- 12.4 cocaine; 109.1 +/- 25.2 cannabis; 114.1 +/- 11.7 drug-free). Alcohol and cigarette use was greater among the cocaine users than among subjects of the recreational drug-free control group (p less than 0.025). Cocaine and the associated lifestyle were not associated with any adverse obstetric or neonatal endpoint (pregnancy weight gain, incidence of delivery complications, gestational age, birth weight, Apgar scores, and rates of major and minor malformations). There were no differences between groups in attaining developmental milestones. Mental and motor scores on the Bayley Scales of Infant Development and Vineland Adaptive Behavior Scales were identical among the three groups, studied at a mean of 19.7 months of age. We conclude that outcome of pregnancy of social cocaine users and subsequent infant physical and cognitive development are within normal limits at 1.6 years of age.