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Association of First-Trimester Echogenicity of the Puborectalis Muscle With Mode of Delivery

OBJECTIVE: To evaluate the association between mean echogenicity of the puborectalis muscle, measured using transperineal ultrasonography, in women during their first pregnancy and the subsequent mode of delivery. METHODS: This is a secondary analysis of a prospective observational study on the association between stress urinary incontinence and levator muscle avulsion after delivery of a first pregnancy. In this study, 280 nulliparous women with singleton pregnancies were examined with transperineal ultrasound examination at 12 and 36 weeks of gestation. Patients were recruited from an obstetrics practice associated with the university medical center in Utrecht, the Netherlands. Mean echogenicity of the puborectalis muscle values were measured at rest, in pelvic floor muscle contraction, and during the Valsalva maneuver. The subsequent mode of delivery was classified into five categories: spontaneous vaginal delivery, instrumental vaginal delivery, elective cesarean delivery, cesarean delivery resulting from nonreassuring fetal status, and cesarean delivery resulting from failure to progress. Mean echogenicity of the puborectalis muscle values according to mode of delivery were compared by analysis of variance and Tukey's post hoc test. RESULTS: Of the 254 women included, 157 had spontaneous vaginal delivery, 47 underwent cesarean delivery (11 elective, 36 emergency), and 45 had vacuum operative vaginal delivery; in five patient files, the mode of delivery was not recorded. Of the analyzed women, those who delivered by cesarean because of failure to progress had a significantly lower mean echogenicity of the puborectalis muscle in pelvic floor contraction at 12 weeks of gestation (mean echogenicity of 116±14) than women who had spontaneous vaginal delivery (132±21; Tukey's post hoc test, P=.03), instrumental vaginal delivery (138±21; P=.004), and cesarean delivery resulting from nonreassuring fetal status (139±20; P=.02). CONCLUSION: Lower mean echogenicity of the puborectalis muscle values in pelvic floor contraction during the first pregnancy at 12 weeks of gestation is associated with subsequent cesarean delivery as a result of failure to progress.