Compared to birth at 39 weeks, elective CD at 37 to 38 weeks has been linked to several neonatal complications.
Alan Tita and his colleagues, who are part of the NICHD Maternal-Fetal Medicine Units Network, recently attempted to better delineate the risks of elective CD at term but prior to 39 weeks.4 They studied over 13,000 women with singleton pregnancies who underwent elective repeat CD at term. The primary outcome was a composite of neonatal death and any of several other adverse sequelae, including respiratory complications, treated hypoglycemia, newborn sepsis, and admission to the neonatal intensive care unit (NICU). As compared with births at 39 completed weeks (>39 0/7), births at 37 and 38 weeks were associated with an increased risk of the primary outcome. The adjusted odds ratio (OR) for adverse outcomes among births at 37 weeks was 2.1 (95% CI; 1.7–2.5) and for births at 38 weeks, it was 1.5 (95% CI; 1.3–1.7). The rates of adverse respiratory outcomes, mechanical ventilation, newborn sepsis, hypoglycemia, admission to the NICU, and hospitalization for 5 days or more were increased by a factor of 1.8 to 4.2 for births at 37 weeks and 1.3 to 2.1 for births at 38 weeks.
The study's most alarming observation was that when the analysis was restricted to the 52% of deliveries that occurred just during the last 3 days before 39 completed weeks (i.e., from 38, weeks 4 days to 38 weeks, 6 days), the risk of complications remained elevated compared with deliveries at 39 completed weeks (RR, 1.21; 95% CI; 1.04–1.40). This suggests that even a few days may make a significant difference. To put this in absolute terms, at 38 weeks, 1.9% of babies had respiratory distress syndrome, 3.9% had transient tachypnea, and over 8% were admitted to the NICU. Tita's research buttresses prior observations that elective CD without antecedent labor is an independent risk factor for respiratory complications in the newborn, and that this risk is increased before 39 weeks.1,5-9