To examine the influence of obesity on obstetric performance, pregnancy outcome, and lactational performance, 163 mostly moderately obese gravidas were compared with age and parity-matched normal weight subjects. Significantly increased incidences of gestational hypertension, inadequate pregnancy weight gain, cesarean section, postpartum infections, and large-for-gestational age infants were observed in the study group. No significant increase in the incidence of diabetes, toxemia, breech presentation, postpartum hemorrhage, infant morbidity or lactational failure was noted in obese women. The mean birth weight of the infants of obese women was 163g greater than that of the control subjects; no difference was observed in infant length or gestational age. These results, while confirming that obesity is an important risk factor, suggest that methodological aspects of the previous studies may have contributed to magnify the severity of the problem.