Anal sphincter electromyography after vaginal delivery: Neuropathic insufficiency or normal wear and tear?

The study was performed to evaluate the: potential role of vaginal delivery on innervation of the external anal sphincter (EAS) muscle. Forty-four wom en, 18 nulliparous and 26 of varying parity (1-4), without genitourinary pr olapse, major urogynecological, anorectal, or neurological dysfunction were included. Participants' histories were evaluated by a questionnaire. Quant itative concentric needle electromyography (EMG) using multi-MUP analysis f or sampling motor unit potentials (MUPs) in all volunteers, and "turn/ampli tude" analysis for interference pattern (IP) analysis in 13 nulliparous and 23 parous women were applied. Pools of MUPs and IPs of parous and nullipar ous women were formed and compared using the Mann-Whitney U test. Multiple linear regression analysis was used for evaluation of parity and obstetric variables. No difference between the groups was found in any MUP parameter, while a significant difference was found in two of five IP parameters. On multiple linear regression analysis, the number of deliveries was related t o several MUP and IP parameters: the time elapsed since last delivery to MU P, and slight stress urinary incontinence to TP parameters. A group of paro us women with (slight) stress incontinence had less "pathologic" MUP parame ters, compared to those without. Vaginal delivery is indeed related to EAS muscle EMG abnormalities. However, these are minor and seem not to indicate loss of sphincter function. Our study casts some doubt on the commonly acc epted preconception that significant damage to peripheral innervation of th e EAS occurs even during uncomplicated deliveries. (C) 2000 Wiley-Liss, Inc .