E1-3. Estimated power for secondary aim #2: We anticipate that at least 630 will consent for and complete the pelvic floor aspects of the study. This will provide adequate power for the key outcomes under secondary aim #2. The rate of POP (defined as any POP at or below the hymen) or FI (based on FISI) in nulliparous women at 6 - 12 months postpartum from prior studies were 20.2% [38] and 12.6%[38, 39], respectively. Using these as baselines, the 630 women will provide >80% power to detect a 40% difference in rates pelvic organ prolapse or fecal incontinence between the two groups. For LAM injury on postpartum 3D transperineal ultrasound examination, a prior study found an average rate of 38% [40]. Using this baseline rate, 630 women will provide >90% power to detect at least a 30% difference in occult LAM injury. For overt anal sphincter injury, the sample size will be sufficient to detect a 40% difference in 2nd, 3rd, or 4th perineal lacerations (anticipated 27% to 16.2% with >80% power).