Pelvic floor damage and childbirth: a neurophysiological study

TLDR

The study examined whether first‑birth vaginal delivery damages the pelvic floor’s striated muscles and nerve supply in nulliparous women. Concentric needle EMG, pudendal nerve conduction studies, and perineometer measurements were used to assess muscle activity and nerve function. EMG showed that 80% of women had partial denervation with subsequent re‑innervation after vaginal delivery, with greater nerve damage in those with prolonged second stage and larger babies, while forceps and tears had no effect; severe denervation was linked to urinary/fecal incontinence and may predispose to prolapse or stress incontinence. Summary.

Abstract

Summary. Ninety six nulliparous women were investigated to establish whether childbirth causes damage to the striated muscles and nerve supply of the pelvic floor. The techniques used were concentric needle electromyography (EMG), pudendal nerve conduction tests and assessment of pelvic floor contraction using a perineometer. There was EMG evidence of re‐innervation in the pelvic floor muscles after vaginal delivery in 80% of those studied. Women who had a long active second stage of labour and heavier babies showed the most EMG evidence of nerve damage. Forceps delivery and perineal tears did not affect the degree of nerve damage seen. We conclude that vaginal delivery causes partial denervation of the pelvic floor (with consequent re‐innervation) in most women having their first baby. In a few this is severe and is associated with urinary and faecal incontinence. For some it is likely to be the first step along a path leading to prolapse and/or stress incontinence.