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Effect of vaginal delivery on the external anal sphincter muscle innervation pattern evaluated by multichannel surface EMG: results of the multicentre study TASI-2

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Abstract

Introduction and hypothesis

A correlation exists between external anal sphincter (EAS) damage during birth and the subsequent development of fecal incontinence. This study evaluated the effect of delivery-related trauma on EAS innervation by means of intra-anal EMG performed with a rectal probe with 16 silver electrodes equally spaced along the circumference, before and after delivery.

Methods

Pre-partum EMG measurements were performed on 511 women, by nine clinical partners from five European countries at the 28th to 34th gestational weeks and the 6th to 8th post-delivery weeks; 331 women returned, after delivery, for the second test. The innervation zones (IZ) of EAS single motor units were identified by means of an EMG decomposition algorithm.

Results

The subjects were divided into four groups according to the delivery mode (Caesarean, vaginal with no evident damage, spontaneous lacerations and episiotomies). The number of IZs before and after delivery was compared. In the 82 women who underwent right mediolateral episiotomy, a statistically significant reduction of IZs was observed, after delivery, in the right ventral quadrant of the EAS (side of the episiotomy). Women who had Caesarean section, spontaneous lacerations or lack of 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. The fast and reliable test proposed indicates the sphincter innervation pattern before delivery and helps obstetricians to evaluate the risks and to choose the preferred side of the episiotomy, if deemed necessary at the time of delivery.

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Acknowledgements

This work was sponsored by Projects TASI (Else Kroner-Fresenius-Stiftung, Compagnia di San Paolo) and TASI-2 (Compagnia di San Paolo). The authors are grateful to Professor Mauro Gasparini for help with statistical analysis, and to Doctors Eleonora Ester Raimondi, Dace Rezeberga, Olesja Zelenova, Pier Dino Rattazzi, Luigi Spagna, Adolf Lukanovic, Anna Maria Paoletti, Donatella Marongiu, Maggiorino Barbero, Vicky Rabino, Lena Martynshyn, Marina Storoshuk, and Milena Ludescher for their help in recruiting patients and taking EMG measurements.

Conflict of interest

None of the authors has any conflict of interest.

Number of authors

Nine clinical institutions and one engineering institution participated in this multicentre study. Six authors are from six clinical institutions and two from the engineering institution that proposed and coordinated the study. A smaller number of authors would strongly penalise institutions that contributed substantially to the multicentre study.

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Correspondence to Roberto Merletti.

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Cescon, C., Riva, D., Začesta, V. et al. Effect of vaginal delivery on the external anal sphincter muscle innervation pattern evaluated by multichannel surface EMG: results of the multicentre study TASI-2. Int Urogynecol J 25, 1491–1499 (2014). https://doi.org/10.1007/s00192-014-2375-0

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  • DOI: https://doi.org/10.1007/s00192-014-2375-0

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