Vaginal birth after cesarean section and levator ani avulsion

Objective: The aim of the study was to assess the risk of levator ani avulsion in vaginal birth after cesarean section (VBAC). Design: Observational cohort study. Settings: Department of Gynecology and Obstetrics, Medical Faculty, Charles University and University Hospital Pilsen. Methodology: In this observational study we included every secundiparous woman after her first VBAC at term from 2012 till 2016 at our tertiary center. Women after repeated VBAC, delivering preterm or women after stillbirth were excluded. In addition, we enrolled random primiparous women as a control group. The women were invited for a 4D pelvic floor ultrasound for acquisition of a 4D volume of their pelvic floor at rest and during Valsalva. The levator avulsion was diagnosed off-line from the volumes of the pelvic floor during contraction, area of the urogenital hiatus was measured at rest and Valsalva. The laterality of the avulsion was additionally noted. The cohorts were then compared using Chi-square test and Wilcoxon two-sample test according to the distribution of normality, p-value < 0.05 was considered statistically significant. Results: Total of 255 women after VBAC in the study period were enrolled in the study based on the inclusion and exclusion criteria. All of them were contacted, 98 (38.4%) came for the examination. The main reason for additional exclusion was another pregnancy or delivery and lack of interest in the study. In addition, 69 random women after first vaginal delivery were examined as a control group. No statistically significant differences in group characteristics apart from the age at the time of birth (32.7 vs. 30.0 years, p < 0.05) were found between VBAC and the Controls. The difference in levator avulsion and ballooning rate did not reach statistical significance. The variance of area of the urogenital hiatus in rest and during Valsalva was similar in both groups. Conclusion: VBAC is not associated with an increased risk of levator ani avulsion compared to primaparous women.