Cesarean sections are now being performed for 31% of deliveries, or 1 of every 3 births, in the United States.1 This cesarean rate is higher than any in our history and shows no sign of slowing down. Much of the rate increase is from repeat cesareans. Pregnant women often believe that 37 to 38 weeks' gestation is the same as 40 weeks', and their obstetricians are accommodating them with scheduled, early operative deliveries. However, this view is not supported by existing evidence, which shows that compared with infants born vaginally those born by cesarean have more adverse respiratory outcomes, especially when delivery occurs before the onset of labor.

To assess the timing of elective cesareans in the United States, and to determine the association between early (before 39 weeks) cesarean and adverse neonatal outcomes, a large prospective study was conducted at 19 centers of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network from 1999 through 2002.1 Among 13,258 women who underwent elective cesareans at "term," 6.3% were at 37 weeks, 29.5% were at 38 weeks, 49.1% were at 39 weeks, and 15% were at 40 weeks or later. Thus, 35.8% of elective cesarean deliveries were performed before 39 weeks of gestation.1 These early deliveries were associated with a significantly increased risk of death, respiratory complications, and admission to the NICU. The authors concluded that elective cesarean deliveries should be delayed until pregnant women complete 39 weeks of gestation.

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