# Success rates of trial of labor after cesarean delivery: the impact of prior vaginal deliveries on outcomes

## TL;DR

This study shows that women who have had a successful vaginal birth after cesarean (VBAC) are more likely to have another successful VBAC, with success rates increasing with prior attempts.

## Contribution

The study provides new evidence that success rates of VBAC increase with the number of prior successful attempts, stabilizing after two.

## Key findings

- VBAC success rates increase from 73.2% with no prior VBAC to 97.0% with five or more prior VBACs.
- Women with at least one prior VBAC have a 5.17-fold higher likelihood of VBAC success.
- Hospitalization duration and blood transfusion risk are lower for women with prior VBAC history.

## Abstract

To estimate the success rates and risks of vaginal birth after cesarean delivery (VBAC) based on the number of prior successful VBACs.

A retrospective cohort study of women with one cesarean section in the past who attempted vaginal delivery between 2013 and 2022, using data from our Medical Center registry. Outcomes were compared based on the number of prior successful VBACs.

Among 2912 deliveries meeting the eligibility criteria, the success rate of VBAC increased with the number of prior VBACs: 73.2% for those with no prior VBAC, rising to 92.3%, 94.7%, 94.0%, and 97.0% for individuals with 1, 2, 3, 4, and 5 or more prior VBACs, respectively. The history of at least one prior VBAC was associated with a 5.17-fold higher likelihood of achieving VBAC success. However, no significant differences in success rates were observed between groups with higher numbers of prior VBACs (≥ 2) compared to individuals with only one prior VBAC. In addition, the duration of hospitalization for both mother and neonate was longer in cases with no prior VBAC history. There was also a higher risk of requiring blood transfusion in the group without a prior history of VBAC.

Women with prior successful VBAC have a high likelihood of achieving another successful VBAC. After two prior VBACs, the success rate remains stable. In addition, women with one or more previous VBACs experience a reduced risk of blood transfusion and shorter hospitalization durations for both the mother and newborn.