Birthweight and pelvic floor trauma after vaginal childbirth

Birthweight seems to be a risk factor for levator ani muscle (LAM) avulsion and a predictive factor for pelvic organ prolapse (POP). Most trauma seems due to first vaginal birth.

One thousand one hundred twenty-five women with at least two vaginal deliveries underwent a physician-directed interview, followed by clinical examination (digital palpation and Pelvic Organ Prolapse Quantification-POPQ) and 4D translabial ultrasound. Ultrasound volume data were obtained at rest, on pelvic floor contraction and Valsalva. The investigator, blinded to all other data, performed offline analysis of the LAM integrity and hiatal area on Valsalva. We tested for associations between birthweight of the first and of the largest vaginally born baby on the one hand and avulsion and symptoms/signs of prolapse on the other hand.

Between July 2014 and July 2017, 1575 patients were seen. After exclusion of nulliparae and women with just one vaginal birth, 1202 remained. Another 77 were excluded due to missing data, leaving 1125. A significant association was found between birthweight and LAM avulsion as well as significant prolapse on POPQ. The birthweight of the first vaginally born baby was at least as predictive for avulsion as the birthweight of any subsequent births, even when adjusted for maternal age at first delivery and use of forceps.

The birthweight of the first vaginally born baby is associated with levator avulsion and subsequent POP. Maximum weight of vaginal births does not seem to be a stronger predictor.