Pregnancies that produced 56,857 children were analyzed to evaluate the relationship of the mothers' relative pregravid body weight to pregnancy outcome. Perinatal mortality rates progressively increased from 37 of 1000 in offspring of thin subjects to 121 of 1000 in the offspring of obese subjects (p less than 0.001). Nearly half of this mortality increase was due to preterm deliveries, particularly before 31 wk of gestation. More than half of the increase in preterm births was caused by acute chorioamnionitis. Other factors that made major contributions to the overall mortality increase were rises in the frequencies of older gravidas (ages 35-50 y), gravidas who had diabetes mellitus, children who had major congenital malformations, and dizygous twins.

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Fourteen of 28 sudden-infant-death syndrome (SIDS) victims had an abnormal proliferation of astroglial fibers in their brain stems and an enlarged mass of chromaffin cells in their adrenal medullas. Both of these abnormalities were associated with greater than normal muscle in the small pulmonary arteries, abnormal brown fat retention, and retained extramedullary erythropoiesis. These latter three findings are probably evidences of chronic alveolar hypoventilation and hypoxemia. The brain stem and adrenal abnormalities are probably also secondary to chronic hypoxemia.