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