Prevalence of levator ani avulsion in a multicenter study (PAMELA study).

Abstract

The objective is to determine the prevalence of levator ani muscle (LAM) avulsion using four-dimensional ultrasound in primiparous women after vaginal delivery and according to delivery mode. This prospective, multicenter study included 322 women evaluated at 6-12months postpartum by four-dimensional transperineal ultrasound to identify levator ani muscle avulsion. The researcher who performed the ultrasound was blinded to all clinical data. Meaningful data about the birth were also recorded: mode of delivery, mother's age and body mass index, duration of second stage, episiotomy, perineal tearing, anesthesia, assistant, head circumference and fetal weight. 303 volumes were valid for evaluation. The overall prevalence of levator ani muscle avulsion was 18.8% (95% CI 14.4-23.2%). In our multivariate analysis, only mode of delivery reached statistical significance as a risk factor for levator ani muscle avulsion (p < 0.001). The prevalence according to the different modes of delivery was 7.8% in spontaneous delivery, 28.8% in vacuum-assisted and 51.1% in forceps-assisted delivery. Compared with spontaneous delivery, the OR for LAM avulsion was 12.31 with forceps (CI 95% 5.65-26.80) and 4.78 with vacuum-assisted delivery (CI 95% 2.15-10.63). Levator ani avulsion during vaginal delivery in primiparous women occurs in nearly one in every five deliveries. Delivery mode is a significant and modifiable intrapartum risk factor for this lesion. The incidence is lower in spontaneous delivery and significantly increases when an instrument is used to assist delivery, especially forceps.