Vaginal birth after Cesarean section and levator ani avulsio
The study states that women having a vaginal birth after cesarean section (VBAC) have an increased rate of levator ani avulsion.

The aim of the study was to explore the risk of levator ani avulsion and levator hiatus enlargement following vaginal birth after cesarean section (VBAC) in comparison to primiparous women after their first vaginal delivery.

In this multicenter observational cohort study, investigators identified all women who had a term VBAC for their second delivery. As a control group, they enrolled a cohort of primiparous women who had their first vaginal birth during the studied period. To increase their control sample they also invited all primiparous women who delivered vaginally. All participants were invited for a 4D pelvic floor ultrasound to assess levator trauma. Levator avulsion and the levator hiatus area at rest and on maximal Valsalva were assessed off-line from the stored pelvic floor volumes during contraction and Valsalva. The laterality of the avulsion was additionally noted.

A total of 301 women had a VBAC for their second delivery during the studied period.

--A significant difference between VBAC and the control group in age, BMI, duration of the first and the second stages of labor at the time of the index birth was observed.

--The levator avulsion rate was significantly higher in the VBAC compared to the control group. The difference was observed dominantly in unilateral avulsions and remained significant after controlling for age and BMI.

--There were no statistically significant differences in the size of levator hiatus at rest or Valsalva.

--The incidence of levator ballooning was comparable in VBAC and Controls.

In conclusion, VBAC is associated with a significantly higher rate of levator ani avulsion compared to the first vaginal birth in nulliparous women. The difference was significant even after controlling for age and BMI.