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

2D USS of the pelvic floor in the 3rd trimester versus mode of delivery

Background: Labour is a complex physiological phenomenon. Existing evidence shows that stretch of the pelvic floor muscles can influence mode of delivery. Aim: To identify properties of the functional female pelvic floor in pregnancy aiding prediction of mode of delivery in women. Methods: A single centre prospective cohort study included 133 pregnant women in 3rd trimester attending antenatal clinic, between November 2014 and August 2015. All women underwent ultrasonographic evaluation of the pelvic floor. The primary outcome was mode of delivery. Measurement obtained by two independent observers blinded to the mode of delivery. ANOVA test used for statistical analysis. Study ethically approved: 14/LO/1718. Results: Analysed 110 cases: nulliparous n=55, P1 (one vaginal birth) n=52, and P1 (one LSCS and planned for VBAC) n= 26.Participants were scanned at average 32 weeks of their pregnancies. Good inter-observer reliability test (kappa 0.75). Trends towards lesser distensibility of the pelvic floor measured as the levator hiatal area were observed in all three examined groups with the VBAC’s pelvic floor being the least distensible. Similar trend was observed in AP diameter between primiparous and VBAC groups. Conclusion: There are trends towards lesser levator ani distensibility in women who were delivered by LSCS