Adding Insult to Injury: Levator Ani Avulsion in Women With Obstetric Anal Sphincter Injuries

In women with obstetric anal sphincter injuries, we compared the rate of major levator ani avulsion after forceps-assisted delivery versus spontaneous vaginal delivery.

Prospective cohort of primiparous women with obstetric anal sphincter injuries. The primary outcome was the rate of major levator ani avulsion as measured by 3-dimensional transvaginal ultrasonography performed between 1 and 2 weeks postpartum. Secondary outcomes included ultrasonographic anteroposterior hiatal diameter, levator hiatal area, and levator-urethra gap, and differences in validated pelvic disorder questionnaires scores at 1 to 2 and 13 weeks postpartum.

Sixty-two women (30 spontaneous deliveries, 32 forceps deliveries) were included in the final analysis. After controlling for delivery variables, women who underwent forceps-assisted delivery were more likely to experience a major avulsion as compared with those who underwent spontaneous delivery (21/32, [65.6%] vs 8/30 [26.7%]; odds ratio, 5.9; 95% confidence interval, 1.5-24.5; P = 0.014). They were also more likely to have larger levator-urethra gaps bilaterally (P = 0.012, 0.016). After controlling for potential confounders, levator ani avulsion was independently associated with persistent anal incontinence symptoms at 13 weeks postpartum (P = 0.02).

In women with obstetric anal sphincter injuries, the risk of levator ani avulsion is almost 6 times higher after forceps-assisted vaginal delivery as compared with spontaneous vaginal delivery. In those with avulsion, recovery of anal continence is compromised, suggesting that adding insult (avulsion) to injury (obstetric anal sphincter injury) may have negative functional consequences.