Inter-delivery Time Interval and the Likelihood of Successful Vaginal Birth After Cesarean Delivery [21P

Abstract

INTRODUCTION: The most commonly utilized prediction models to assist in the prediction of vaginal birth after cesarean delivery (VBAC) have not included inter-delivery time interval as a contributing variable. Therefore, we sought to determine the association of inter-delivery time interval and rate of successful VBAC. METHODS: This retrospective cohort study utilized the United States Natality Live Births database from the Center for Disease Control and Prevention for the years 2016–2017. Singleton patients at term with their second pregnancy and live birth undergoing a trial of labor after one prior cesarean delivery (TOLAC) were eligible for inclusion. The inter-delivery time interval, defined as the time elapsed between live births, was divided into 7 groups by months: 12–17, 18–23, 24–35, 36–47, 48–59, 60–71, 72 and beyond. Pearson's Chi-Squared test was used to compare rates of successful VBAC across the different inter-delivery time interval groups. Statistical significance was determined as P<.05. RESULTS: Of the 60,526 women who underwent TOLAC, 39,948 (66%) had a VBAC. The highest rate of VBAC success was seen with an inter-delivery time interval of 24 to 35 months (12,368/17,760; 69.6%). The differences in rates of VBAC between the different time intervals were statistically significant (P<.0001). CONCLUSION: Overall, the rate of successful VBAC in the United States among cases from 2016–2017 was 66%. Our data indicate that the rate of successful VBAC is affected by the inter-delivery time interval, with the optimal time for VBAC being 24–35 months after cesarean delivery. The clinical implication of this statistical finding requires further study.