Evaluation of child delivery trauma on anal sphincter muscle by means of surface electromyography (Results of the multicenter study TASI-2)

Začesta, Vita and Zelenova, Olesija and Drusany-Starič, Kristina and Raimondi, Eleonora Ester and Martsidis, Konstantinos and Protsepko, Oleksander and Baessler, Kaven and Cescon, Corrado and Merletti, Roberto (2014) Evaluation of child delivery trauma on anal sphincter muscle by means of surface electromyography (Results of the multicenter study TASI-2). In: The Journal of Maternal-Fetal and Neonatal Medicine Updated on April 28 th , 2014 XXIV European Congress of Perinatal Medicine, 4-7 Jun 2014, Florence, Italy.

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Introduction. Recent studies demonstrated that there is a significant correlation between anal sphincter damage during vaginal birth, with or without episiotomy, and subsequent development of anal incontinence in women. Functional asymmetry of pelvic floor innervation has been shown to exist in healthy subjects. The asymmetry of sphincter innervation is strongly associated with postpartum incontinence in those cases in which the trauma occurs on the dominant side of innervation. Episiotomy is the most common obstetric surgical intervention; right side mediolateral episiotomy is usually recommended. The damage of pudendal nerve during episiotomy could lead to anal sphincter mass decrease and anal incontinence. The symptoms may appear many years after delivery. Pre-emptive location of innervation zones (IZs) with anal sphincter electromyography (EMG) could allow choosing the least invasive side for episiotomy. Avoiding the incision of IZs would presumably reduce the incidence of anal incontinence. Study aim. The aim of the study is to validate the surface EMG as a screening tool to locate the IZs of anal sphincter, and to evaluate the effect of episiotomy related trauma on the external anal sphincter muscle. Methods. In this prospective cohort study, 511 pregnant primiparous women, by nine clinical partners from five European Countries, were involved and surface EMG was performed to detect the distribution of IZs of external anal sphincter. EMG measurements were performed at the 28th - 34th gestational week and 6-8 post-delivery week (end of puerperium). The study was conducted in double blind, meaning that the clinical partners did not receive any information regarding the IZs of the patients and the signal analysis was performed without having information regarding the type of delivery. Results. 331 women returned, after delivery, for the second test. The subjects were divided in four groups according to the delivery mode (Caesarean, vaginal with no evident damage, spontaneous lacerations and episiotomies). The numbers of IZs were compared before and after delivery. In the 82 women who underwent right mediolateral episiotomy, a statistically significant reduction of IZs was observed (mean=0.62, 95%CI [-1.03:-0.21]), after delivery, in the right ventral quadrant (side of episiotomy) of the EAS (external anal sphincter ), while women who had Caesarean section, spontaneous lacerations or no evident damage did not present any significant change in the innervation pattern. Conclusions. Right episiotomy reduces the number of IZs on the right-ventral side of the EAS. Knowledge of the pre-partum distribution of IZs allows obstetricians choose the side where to perform episiotomy (in case it would be necessary at the time of delivery) in order to avoid iatrogenic damage of pudendal nerve. This knowledge, which can be obtained with a disposable probe and a minimally invasive surface EMG pre-partum test, is expected to reduce the consequences of episiotomy and subsequently minimize the risk of anal incontinence.

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