A retrospective study of 343 women who lacked prenatal care was conducted to ascertain the effect of recent cocaine abuse on birth weight and gestational age. All pregnant women admitted in labor to a large urban teaching hospital between January 1 and December 31, 1986 who had not received prenatal care were included. The charts of these women were evaluated to obtain information about medical and obstetric complications of pregnancy, labor and delivery, and birth weight and gestational age of the infant. Information about drug use was obtained by urine toxicology at the time of admission. Results of ordinary least-squares multiple regression analyses indicated cocaine abuse to be a significant predictor of low birth weight and early gestational age. No correlation was found between cocaine abuse and abruptio placentae or maternal hypertension.