Intrapartum cesarean delivery in nulliparas: Risk factors compared by two analytical approaches

Abstract

OBJECTIVE: To determine risk factors for cesarean delivery in nulliparas at labor admission. STUDY DESIGN: Nulliparas with live-born, singleton gestations ≥37 weeks in spontaneous or induced labor were analyzed from the Consortium on Safe Labor database in a retrospective observational study. Classification and regression tree (CART) and multivariate logistic regression analysis determined risk factors for cesarean delivery. RESULT: Of the 66 539 nulliparas, 22% had a cesarean delivery. In the CART analysis, the first cervical dilation exam was the first branch followed by body mass index (BMI). Cesarean deliveries occurred in 45%, 25%, 14% and 10% of deliveries at <1 , 1 to 3, 4 and ≥ 5 cm dilated, respectively. The BMI influence was most evident in the o1 cm dilation category with 26% of BMI <25 kgm-2 and 66% of BMI ≥ 40 kgm- 2 having a cesarean delivery. The fewest cesarean deliveries (5%) occurred in those ≥5 cm and BMI <25 kgm-2. In the multivariate regression analysis, first cervical dilation exam <1 cm (odds ratio (OR) 5.1, 95% confidence interval (CI): 4.5 to 5.7; reference ≥5 cm) and BMI ≥ 40 kgm-2 (OR 5.1, 95% CI: 4.6 to 5.7; reference BMI <25.0 kgm-2) had the highest odds for cesarean delivery. CONCLUSION: Cervical dilation on admission followed by BMI were the two most important risk factors for cesarean delivery identified in both CART and multivariate regression analysis.