We sought to determine the contribution of elective delivery to severe respiratory distress syndrome (RDS) on a weekly basis from 37-40 weeks' gestation. Chart reviews confirmed gestational age, delivery reason, and primary diagnosis of all inborn neonates with RDS requiring mechanical ventilation delivered at 37 0/7-40 6/7 weeks' gestation from 1/1/90-12/31/99. Exclusion criteria were sepsis, pneumonia, meconium aspiration, asphyxia, pulmonary hemorrhage, hydrops, chromosomal abnormality, or congenital malformations affecting respiration. Thirty-five thousand and thirty-one deliveries occurred from 37 0/7-40 6/7 weeks; 18 (0.05%) had RDS requiring mechanical ventilation. Nine infants delivered at 37 0/7-37 6/7 weeks, (OR for RDS = 38.5; 95% CI = 8.3, 178.3), seven delivered at 38 0/7-38 6/7 weeks, (OR for RDS = 13.3; 95% CI = 2.8, 64.0), and two delivered at 39 0/7-40 6/7 weeks. Six of 18 infants were electively delivered without documented lung maturity. Infants born at 37 0/7-38 6/7 weeks are at significantly increased risk for severe RDS. One third of RDS cases were potentially avoidable.