Pubococcygeus-puborectalis trauma after forceps delivery: evaluation of the levator ani muscle with 3D/4D ultrasound.

Introduction and hypothesis: This study seeks to assess the effects of forceps-assisted delivery on the levator hiatus.

Methods: Seventy-six women were investigated 12 months after forceps-assisted delivery. Introital three-/four-dimensional ultrasound measured volumes at rest and during the Valsalva maneuver. Morphological parameters analyzed were angle gamma, hiatal area, pubovisceral angle, and continuity between the muscle and pelvic sidewall. Avulsion was diagnosed by loss of continuity.

Results: Forty-eight women had avulsion injuries, 23 had bilateral, and 25 had unilateral. Bilateral avulsion increased hiatal area during straining and at rest and was associated with changes in bladder neck position at rest. Unilateral avulsion injury was associated with a higher pubovisceral angle on the side of the avulsion.

Conclusion: Forceps-assisted vaginal delivery is associated with levator ani injury. Avulsion of the pubovisceral muscle seems more common after forceps delivery than after spontaneous vaginal delivery. Avulsion alters hiatal shape and area and influences the position and mobility of the anterior compartment.