Even at Term, Timing Of Cesarean Is Linked To Adverse Outcomes

Lisa Melhado, Guttmacher Institute

First published online:

| DOI: https://doi.org/10.1363/4113009

The timing of elective repeat cesarean section, even for term births, may have important implications for infant heath, according to a large, multicenter study conducted in the United States.1 When compared with infants delivered by elective repeat cesarean section at 39 weeks' gestation, infants delivered at 37 weeks' and 38 weeks' gestation are at increased risk for a range of adverse outcomes, including death, respiratory complications and admission to the neonatal intensive care unit (odds ratios, 1.3–4.2).

Infants delivered by cesarean are at increased risk for adverse neonatal outcomes, even when they are delivered at term (i.e., at 37 weeks' gestation or later). Furthermore, elective delivery before 39 weeks' gestation generally is not recommended unless there is evidence of fetal lung maturity. Therefore, researchers sought to describe the timing of elective repeat cesarean deliveries and to assess the associations between the risk of adverse neonatal outcomes and such deliveries at term but before 39 weeks. Using data from a network of 19 academic centers, they identified 24,077 women who delivered a viable infant by repeat cesarean section in 1999–2002; gestational age was determined by the date of the woman's last menstrual period or by the results of the earliest ultrasound. Women with medical conditions that would warrant early delivery and those with multiple gestations or a fetus with a major congenital defect were excluded; the final sample consisted of 13,258 women.

The primary outcome was a composite of any adverse outcome, including death, respiratory distress syndrome or rapid and labored breathing, admission to the neonatal intensive care unit, newborn sepsis, hypoglycemia, cardiopulmonary resuscitation or ventilation in the first 24 hours after birth, and hospitalization for five or more days. The infants were followed for 120 days or until they were discharged from the hospital. Using logistic regression to adjust for maternal age, race or ethnicity, marital status, number of previous cesarean sections, insurer, and whether the woman had smoked or had had gestational diabetes, the researchers determined the associations between adverse neonatal outcomes and gestational age at delivery.

Six percent of women who had an elective repeat cesarean delivery at term did so at 37 weeks of gestation; 30% did so at 38 weeks, 49% at 39 weeks and 15% at 40 weeks or later. Compared with women who delivered at 39 weeks' gestation, those who delivered earlier were older; had a lower body-mass index at delivery; and were more likely to be white, to be married, to have private insurance and to have had two or more cesarean sections. As the infants' gestational age increased, so did their mean birth weight.

The incidence of the primary outcome was 11% among all infants; it was 8% among infants delivered at 39 weeks' gestation, 11% among those delivered at 38 weeks' and 15% among those delivered at 37 weeks' gestation. The incidence of the primary outcome and of any adverse outcome decreased as gestational age increased from 37 to 39 weeks; these trends remained significant even after adjustment for confounders. Compared with infants delivered at 39 weeks, infants delivered at 37 weeks had higher odds of the primary outcome (odds ratio, 2.1) and any adverse outcome (1.8–4.2); for infants delivered at 38 weeks, the adjusted odds ratio was 1.5 for the primary outcome and 1.3–2.1 for any adverse outcome. Delaying delivery until 39 weeks might have reduced the occurrence of any adverse outcome by 48% among infants delivered at 37 weeks' gestation and by 27% among those delivered at 38 weeks'.

More than one-third of all elective repeat cesarean deliveries examined in the study occurred before 39 weeks of gestation. According to the researchers, "these early deliveries are associated with a preventable increase in neonatal morbidity and admissions to the neonatal [intensive care unit], which carry a high economic cost." They believe their "findings support recommendations to delay elective delivery until 39 weeks of gestation and should be helpful in counseling." —L. Melhado


1. Tita ATN et al., Timing of elective repeat cesarean delivery at term and neonatal outcomes, New England Journal of Medicine, 2009, 360(2):111–120.