Impact of Pushing Timing on Occult Injury of Levator Ani: a Multicenter Randomized Controlled Trial

Abstract

The impact of the timing of pushing during the second stage of labor on pelvic floor disorders is unknown. We sought to determine whether immediate or delayed pushing is associated with an increased proportion of injury to the levator ani after a first delivery among nulliparous women. The Optimizing Management of the Second Stage (OMSS) study was a multicenter randomized trial. Nulliparous women with term pregnancies and neuraxial analgesia were randomly assigned at complete cervical dilation to either immediate pushing or delay for 1 hour. Consenting participants underwent longitudinal pelvic floor assessments (PFA): 1) during postpartum stay (baseline); 2) at 6 weeks (PP1); and 3) at 6 months (PP2) postpartum. Eligible participants underwent transperineal 3D ultrasounds at each visit. Following the completion of all visits by all subjects, saved 3D ultrasound volumes were assessed in a masked fashion. The outcome was complete (but “occult”) levator ani muscle (LAM) injury on the right or left, defined as a widening of the attachment of the levator ani (beyond a set threshold in three contiguous slices) to its origin (Figure) utilizing the Levator Urethra Gap (LUG) measurement. The impact of an alternative threshold LUG distance was explored. Measurements and proportions were compared between the two groups. Of the 2414 subjects randomized, 941 (39.0%) participated in the PFA; 452 in the immediate pushing and 489 in the delayed pushing groups. Ultrasounds were performed on 67%, 83%, and 77% of the PFA participants at the baseline, PP1 and PP2 visits respectively. Demographic and labor characteristics (previously reported) were comparable between the 2 groups; 94% were non-Hispanic and 50% were Black participants. At all 3 timepoints, there were no differences in LAM injury (Table). These findings did not change when the threshold (sensitivity) of LAM injury was adjusted. Among nulliparous women at term with neuraxial analgesia, neither immediate nor delayed pushing in the second stage resulted in significant differences in occult LAM injury.View Large Image Figure ViewerDownload Hi-res image Download (PPT)