The levator ani muscle during pregnancy and major levator ani muscle defects diagnosed postpartum: a three- and four-dimensional transperineal ultrasound study.

ABSTRACT

OBJECTIVE: To investigate associations between levator hiatus area and levator ani muscle function during pregnancy and major levator ani muscle defects postpartum. DESIGN: Observational prospective cohort study. SETTING: University hospital, Norway. SAMPLE A cohort of 234 nulliparous women at 21 and 37 weeks of gestation, and at 6 weeks postpartum. METHODS: Ultrasound measurements of the levator hiatus at rest, during pelvic floor muscle contraction, and during the Valsalva manoeuvre were taken at 21 and 37 weeks of gestation. Levator ani muscle function was estimated as the percentage changes in levator ani muscle length from rest to contraction, and the level of muscle stretch during the Valsalva manoeuvre. Major levator ani muscle defects were diagnosed at 6 weeks postpartum using tomographic ultrasound imaging. MAIN OUTCOME MEASURES: Associations between ultrasound measurements antepartum and major levator ani muscle defects postpartum. RESULTS: Women with major levator ani muscle defects postpartum had significantly smaller levator hiatus area at rest and during the Valsalva manoeuvre at mid-pregnancy (mean difference 1.03 cm(2) , 95% CI 0.31-1.76; 2.92 cm(2) , 95% CI 1.77-4.07), and at 37 weeks of gestation (mean difference 1.47 cm(2) , 95% CI 0.62-2.32; 2.84 cm(2) , 95% CI 0.88-4.80), than women without such defects. They also had significantly less shortening of the levator ani muscle during contraction at 37 weeks of gestation. CONCLUSIONS: Smaller levator hiatus area at rest and during the Valsalva manoeuvre at mid and late pregnancy, and less shortening of the levator ani muscle during contraction at 37 weeks of gestation, are associated with major levator ani muscle defects postpartum.