Abstract
Objective The study aims to reduce cesarean rates, eligible women are being offered an option
of vaginal birth after cesarean (VBAC). However, little data exist regarding efficacy
of amniotomy as a tool in this population. We sought to evaluate the impact of early
amniotomy on VBAC success.
Study Design This is a secondary analysis case-control study using the MFMU (Maternal-Fetal Medicine
Units Network) Cesarean Registry. Women were included if they had a singleton pregnancy,
were attempting VBAC, and underwent induction with artificial rupture of membranes.
Cases were defined as subjects with successful VBAC; controls were defined as subjects
with failed trial of labor after cesarean (TOLAC). Early amniotomy was defined as
amniotomy at <4 cm. Demographic and obstetric characteristics were compared and multivariate
logistic regression was performed.
Results A total of 1,490 women were included. Early amniotomy occurred in 59.5% with VBAC
versus 63.2% with failed TOLAC (p = 0.24). After controlling for body mass index, prior vaginal delivery, African–American
race, labor length, gestational age, birthweight, epidural use, Foley catheter balloon
ripening, induction method and oxytocin use, early amniotomy was associated with a
34% decrease in VBAC success (p < 0.01). Women who had early amniotomy did not have higher rates of chorioamnionitis
(2.8 vs. 2.9%, p > 0.99).
Conclusion Unlike data from nulliparous women, our data suggest that induction with early amniotomy
does not increase the likelihood of VBAC.
Keywords
induction - amniotomy - TOLAC - vaginal birth after cesarean
