We compared pregnancy outcome in 286 teenaged primigravidas (less than or equal to 16 years old) and 267 adult primigravidas (21 to 25 years old) who had similar prenatal care, socioeconomic status, and racial balance. The incidence of preterm labor and delivery of a low birthweight infant was significantly higher in the teenagers. The incidence of preeclampsia was significantly higher in the adults. Cesarean delivery was not done more frequently in teenagers, nor was there a higher incidence of infants small for gestational age, anemia, and abnormal presentation in labor. The birthweight of infants of black teenagers was significantly lower than the birthweight of those of white teenagers, and overall birthweight was significantly lower in infants of teenagers than those of adults. Although prenatal care, socioeconomic factors, and racial balance were comparable for young teenagers and adults, teenagers were still at a significantly greater risk for delivery of smaller infants, preterm labor, and low birthweight infants.