Between June 26, 1985, and Feb. 24, 1989, 101 seropositive pregnant women and 129 seronegative pregnant women from the same prenatal clinics in Brooklyn and the Bronx were recruited into a prospective study of human immunodeficiency virus infection in pregnant women and their offspring. This report details the course of pregnancy and short-term neonatal outcomes of 91 seropositive women and 126 seronegative women who gave birth during the study period. Seropositive mothers were significantly more likely to have sexually transmitted diseases (17.6% vs 7.1%, p = 0.017) and medical complications (43.0% vs 25%, p = 0.006) during pregnancy. No other obstetric complications (e. g., chorioamnionitis, endometritis, toxemia, or placental problems) were associated with serologic status. After controlling for confounding variables (drug use, tobacco use, age of mother, and clinic), we found that the mother's serologic status was not significantly associated with birth weight, gestational age, head circumference, or Apgar scores among live infants. For example, after adjustment on confounders we found that children born to seropositive mothers weighed about 7 gm more than children of seronegative mothers (95% confidence interval, -180 to 194 gm). We conclude that in this population human immunodeficiency virus infection has little demonstrable impact on the status at birth of live neonates.