Vaginal delivery may lead to trauma of levator ani muscle

Vaginal delivery may cause significant pelvic floor trauma in as many as one-third of first-time deliveries. This trauma appears, upon ultrasound, to primarily affect the levator ani muscle.

As part of a prospective, observational study, Australian investigators examined 63 nulliparous women at 36 to 40 weeks' gestation using 3-D/4-D translabial ultrasound. The women were asked to return 2 to 6 months after giving birth for a second ultrasound, said lead author Hans Peter Dietz, MD, associate professor of obstetrics and gynecology at the University of Sydney, who presented the data here on Thursday.

Patients were considered to have avulsion of the pubovisceral muscle when they showed a loss of continuity between the muscle and pelvic sidewall in volume datasets that were obtained at rest, on levator contraction, and on Valsalva. When the diagnosis was in doubt, the investigators directly compared antenatal- and postnatal-rendered volumes and axial plane single frames.

Overall, 50 of the original 63 women returned for a second ultrasound 2 to 6 months after childbirth. Among these women, 39 had given birth vaginally, and a full 36% of these women had a levator avulsion. None of the 11 women who delivered by cesarean section had defects.

"Out of 39 women who delivered vaginally, there were 14 who had significant changes to the levator ani. The prevalence was more than twice as high as expected," Dr. Dietz said.

The presence of defects was significantly associated with higher maternal age, and there were also nonsignificant trends toward an association with vaginal operative delivery and worsened stress incontinence postpartum. Bladder neck descent was dramatically increased postpartum, particularly among those with defects.

Dr. Dietz believes that the association between age at first delivery and pelvic floor damage is particularly disturbing, as women all over the world are having their first children later and later in life.

"It now seems that, if you do manage to avoid a cesarean, [older women are] more likely to suffer damage to the pelvic floor muscle than younger women," he told Urology Times. "In future research, we'll have to work out how to detect women most at risk of such damage and how to stop the trauma from occurring. This may not necessarily involve planned cesarean delivery. I think it is likely that there will be other ways of protecting the pelvic floor."