Maternal and neonatal outcomes according to timing of planned elective cesarean section in non-complicated singleton pregnancies

Background: The objective of this study was to compare maternal and neonatal outcomes in women with non-complicated singleton pregnancies according to timing of planned elective cesarean section (CS). Methods: This was a retrospective cohort study of 2,365 women with singleton pregnancies who were planned for elective CS at term pregnancy in a single institution between 2010 and 2021. Pregnant women with preterm delivery, multiple gestation, vaginal delivery, complicated pregnancy, or non-scheduled emergency CS were excluded. Subjects were categorized into three groups according to planneddate of CS: 37 (37+0‒37+6) weeks (n = 147), 38 (38+0‒38+6) weeks (n = 1,486), and 39 (39+0‒39+6) weeks (n = 732) of gestation. Primary outcomes of this study were emergency CS rate and maternal and neonatal composite morbidity. Results: The rate of emergency CS significantly increased with an increase in planned week of CS. After controlling for confounding factors, the rate of emergency CS significantly higher in the 38-week group (adjusted odds ratio (aOR): 4.70, 95% confidence interval (CI): 1.71‒12.95) and the 39-week group (aOR: 8.78, 95% CI: 3.16‒24.37) than in the 37-week group. The rate of maternal composite morbidity (aOR: 3.22, 95% CI: 1.65‒6.32) was significantly higher in the 37-week group, but not in the 38-week group, than in the 39-week group. Rates of neonatal ventilator use and respiratory distress syndrome significantly decreased, whereas neonatal meconium staining significantly increased with an increase in planned week of CS. The rate of neonatal composite morbidity (aOR: 2.69, 95% CI: 1.22‒5.96) was significantly higher in the 37-week group, but not in the 38-week group, than in the 39-week group. Conclusion: In non-complicated singleton pregnancy, planning elective CS at 37 weeks of gestation was associated with a higher risk of adverse pregnancy outcome. However, planning elective CS at 38 weeks of gestation showed no worse pregnancy outcome than that at 39 weeks of gestation.