712: Intrapartum variables predicting labor progress and vaginal delivery in trials of labor after cesarean

Abstract

Although models predicting vaginal birth after cesarean (VBAC) are available, less is known about how intrapartum factors influence the outcome of trial of labor after cesarean (TOLAC). The purpose of this study was to investigate intrapartum variables associated with achieving vaginal delivery after cesarean. We performed a retrospective cohort study of patients undergoing TOLAC at an academic tertiary institution between 2011 and 2018. Term, singleton pregnancies with 1 prior cesarean were included. Our primary outcome was successful VBAC. Secondary outcomes were entering active labor (6 cm) and second stage of labor (10 cm). We performed univariate analysis of maternal and intrapartum characteristics. Delivery after November, 2014, was a measure of outcomes following the Consortium on Safe Labor. Multivariate logistic regression was performed to identify predictors of a woman entering active labor, second stage, and successful VBAC. A total of 984 patients met inclusion criteria. Of those, 844 (86%) achieved active labor, 758 (77%) achieved second stage, and VBAC occurred in 717 (73%). Multiple maternal and intrapartum differences were identified between groups (Table 1), and remained predictive of achieving active labor and second stage in regression analysis. However, only BMI, duration of active labor and second stage, and chorioamnionitis were associated with VBAC in those who reached second stage of labor. In multivariate logistic regression, delivery after the Consortium on Safe Labor was predictive only of achieving active labor (OR 1.66). Although there were multiple predictors of attaining active labor and second stage, only a BMI ≥39.5, active labor ≥ 7 hours, 2nd stage ≥ 1.5 hours, and chorioamnionitis predicted VBAC failure in those achieving second stage (Table 2). Although numerous factors predicted whether a woman would reach active labor and second stage, as patients progress in labor, only intrapartum variables predicted VBAC. In addition to antepartum factors, clinicians should consider normal progression of labor a strong predictor of VBAC.View Large Image Figure ViewerDownload Hi-res image Download (PPT)