Maternal age at delivery and intrapartum cesarean delivery risk in a large contemporary term birth cohort

Background Cesarean delivery rates and maternal age at delivery have both increased in the United States. Although maternal age has been associated with cesarean delivery, the extent to which this association persists after adjustment for measured confounders remains clinically relevant, particularly at very advanced maternal ages.Objective To evaluate the association between maternal age at delivery and risk of intrapartum cesarean delivery.Study Design Multicenter retrospective cohort study of live births in a large integrated healthcare system (2012–2022). We excluded preterm deliveries (<37 weeks gestation), multifetal gestations, scheduled cesarean deliveries, patients with inadequate prenatal care (<4 prenatal visits), and those not between the ages of 18–60. Logistic regression was used to adjust for race and ethnicity, parity, body mass index (BMI), hypertension, pre-eclampsia, gestational diabetes, pre-gestational diabetes, fetal distress, fetal growth restriction, large for gestational age fetuses, macrosomia, chorioamnionitis, meconium staining, and pregnancies resulting from assisted reproductive technology. Cesarean delivery risk was compared across 5-year age intervals using ages 25–34 as the reference group.Results Among 328,145 participants, cesarean delivery rates increased progressively with advancing age. The cesarean delivery rate in the reference group was 16.1%. Compared with the reference group ages 25–34, ages 18–24 had lower odds of cesarean delivery (13.0%; aOR 0.70, 95% CI 0.68–0.72), while odds were higher among ages 35–39 (20.7%; aOR 1.44, 95% CI 1.40–1.47), 40–44 (25.7%; aOR 1.89, 95% CI 1.81–1.97), 45–49 (33.5%; aOR 2.60, 95% CI 2.23–3.04), and 50–60 (50.0%; aOR 4.56, 95% CI 2.57–8.09).Conclusion Maternal age is associated with intrapartum cesarean delivery risk after adjustment for measured confounders. The association was progressive across age strata. These findings may inform counseling and delivery planning and underscore the need for future work addressing cesarean indications and additional obstetric confounders.