To assess whether a history of prior cesarean delivery is associated with an increased risk of earlier delivery timing and resultant neonatal morbidity.
We performed a population-based retrospective cohort study using U.S. birth certificate data, 2012–2016. The study population included women with one or more prior cesarean deliveries compared with a referent group of parous women without prior cesarean delivery. To enrich for a population with minimized risk factors for early delivery, we excluded women with history of preterm birth, pregnancies complicated by multifetal gestation, pregnancy-induced hypertension, anomaly, small for gestational age, or malpresentation. Analyses were limited to births from 35 to 42 weeks of gestation. Women with a vaginal birth after cesarean delivery were excluded. The primary outcome was the risk of birth at each week of gestational age. Secondary outcomes included adverse neonatal and maternal outcomes.
Patients were stratified by number of prior cesarean deliveries (one, two, three, or four or more) compared with parous patients without prior cesarean delivery. The adjusted relative risk (aRR) of delivery at 35 weeks of gestation was highest in women with four or more prior cesarean deliveries (aRR 2.79, 95% CI 2.74–2.82). Prior cesarean delivery also had a significant influence on neonatal morbidity. As the number of prior cesarean deliveries increased, the risk of composite neonatal morbidity increased, from 8.0% (aRR 1.5, 95% CI 1.48–1.51) with one prior cesarean delivery up to 21.0% (aRR 4.9, 95% CI 4.76–5.04) with four or more prior cesarean deliveries compared with a baseline risk of 5.5% in parous women without prior cesarean delivery.
Prior cesarean delivery is correlated with earlier delivery and increased neonatal morbidity. Advocating trial of labor after cesarean delivery may provide maternal and neonatal benefit.