Change in prevalence of major levator ani muscle defects from 6 weeks to 1 year postpartum, and maternal and obstetric risk factors: A longitudinal ultrasound study.

Abstract

The present study aimed first to investigate the change in prevalence of major levator ani muscle (LAM) defects, also called avulsions, from 6weeks to 1year postpartum, and second to assess maternal and obstetric risk factors for having persistent major LAM defects/avulsions at 1year postpartum. This is a secondary analysis of data from a prospective cohort study including 300 nulliparous women at 17-19weeks of gestation. Major LAM defects were diagnosed at 6weeks and 1year postpartum using transperineal ultrasonography. We defined persistent major LAM defects as a defect diagnosed both at 6weeks and 1year postpartum. Maternal and obstetric data were obtained from the hospital's electronic birth records. Pelvic floor muscle function was measured vaginally by manometer at 21weeks of gestation. The main outcome measurement was change in prevalence of major LAM defects. Maternal and obstetric risk factors for having persistent major LAM defect were also assessed. Prevalence of major LAM defects was 19.4% at 6weeks and 10.4% at 1year postpartum. No new major LAM defects were diagnosed at 1year postpartum. Persisting major LAM defects were associated with longer second stage of labor (median 74.5minutes vs median 48.0minutes, P=.012) and higher neonatal birthweight (mean difference of 232.3g, 95% confidence interval [CI] 21.5-443.1). Vacuum delivery was independently associated with persistent major LAM defects, adjusted OR 3.0 (95% CI 1.0-9.0). There was a 50% reduction of sonographically diagnosed major LAM defects from 6weeks to 1year postpartum. This finding suggests that assessment of the major LAM 6weeks postpartum may be too early to diagnose defects/avulsions. Long second stage of labor, high neonatal birthweight and vacuum delivery were associated with persistent major LAM defects/avulsions.