Recommended gestational weight gain is based on supplying adequate nutrition to the conceptus, ensuring normal growth and development. Since morbidly obese women have an overabundance of nutrients for fetal transfer, we examined the effects of weight gain on fetal outcome in women greater than 160% of ideal body weight. Gestational weight gains varied from -18 to +64 pounds, allowing analysis of fetal outcome based on maternal weight gain. No correlation between maternal weight gain and ketonuria, birthweight or length, placental weight, or Apgar scores was noted. Gestational age at delivery was inversely related to weight gain. When grouped by maternal weight gain, fetal outcome was no different if mothers gained less than or greater than 10 pounds. We conclude that limited weight gain in the morbidly obese women does not adversely affect fetal outcome, and prospective trials of limited weight gain diets in morbidly obese women are warranted.