Feasibility study for the value of pelvic floor distension in predicting mode of birth for women undergoing Vaginal Birth After Caesarean

INDRODUCTION & HYPOTHESIS: Women having Vaginal Birth (VB) have different soft tissue dynamics to women requiring emergency Lower Section Caesarean Section (LSCS). AIMS: To assess the role of ultrasound in the assessment of LH distensibility in predicting outcomes for women wishing for Vaginal Birth After Caesarean section (VBAC). To inform subsequent trial design including understanding womens attitudes to the use of ultrasound in prediction of vaginal birth METHODS: Nulliparous, previous VB and previous LSCS underwent a transvaginal ultrasound. This scan looked at the distensibility of the LH and then correlated with mode of birth. Analysis used logistic regression and ROC curves analysis for static measurements and distensibility. A second cohort was also asked about their views as to the usefulness of such a tool to help inform on the utility of such a model. RESULTS: The original hypothesis confirmed maternal BMI, Anterior Posterior (AP) diameter at rest and AP distensibility all being significant predictors of VB in nulliparous women. As expected this relationship was also seen in women who had previously had a vaginal birth. Of the VBAC group, 23 women had LSCS. Five were Robson category, 18 had emergency LSCS in labour. 25 women had VB. Whilst there were trends towards lesser distensibility in VBAC women who delivered vaginally, none of these reached sgnificance. The concept of the use of scanning to inform women as to likelihood of successful vaginal birth was supported by the survey. CONCLUSION: Previously noted characteristics in nulliparous women for pelvic floor distension were confirmed. This relationship was not demonstrated for the VBAC cohort. We were unable to establish criteria for a simple ultrasound model to predict VB in women wishing for VBAC. Overall, women would welcome such model if it were available.