Abnormal pregnancies (33 per cent) were studied in 417 consecutive, unmarried, primiparous women, age 12 to 18 years (black, 54 per cent; white, 46 per cent). Black patients had no increase in abnormal pregnancies but had more infants weighting less than 2,500 grams (p less than 0.01). Black patients with pre-eclampsia gained less weight than white patients (24 versus 34 pounds, p less than 0.05) and had smaller infants (2,834 versus 3,316 grams). In white patients, the mean age at menarche was earlier in women who lost their infants (11.0 versus 12.7 years; p less than 0.01). Smoking was more prevalent in normal pregnancies (47 per cent) than abnormal pregnancies (38 per cent). Spontaneous abortion and fetal loss occurred more often in smokers (p less than 0.01). White women smoked more than blacks (60 versus 37 per cent). In mothers of infants weighting less than 2,500 grams, there were fewer smokers. Unexpectedly, smokers had less hypertension and pre-eclampsia. Human chorionic somatomammotropin values correlated with infant size. Levels of less than 4 mug per milliliter after 30 weeks' gestation were identical in normal and abnormal pregnancies (4.4 per cent). They were associated with small infants but no fetal deaths and did not predict outcome of pregnancy.