Risk Factors for Intrapartum Anorectal Mucosal Lacerations and Rectovaginal Fistula: A Retrospective Comparative Study.

INTRODUCTION

We examined the risk factors for fourth-degree perineal lacerations (intrapartum anorectal mucosal lacerations) and rectovaginal fistulas as one of the later complications.

METHODS

We reviewed the obstetric records of all singleton vaginal deliveries after 22 weeks of gestation at our institute between January 2006 and December 2018 (n = 19,370).

RESULTS

Of the 19,370 deliveries, 61 had fourth-degree perineal lacerations (0.31%). Of the 61 women, 5 (8.2%) developed rectovaginal fistulas 2-3 weeks after their deliveries. Upon multivariate analysis, nulliparity (Adjusted odds ratios (OR) 3.58, 95% confidence interval (CI) 1.6-8.1, p < 0.01), midline episiotomy (Adjusted OR 2.10, 95% CI 1.0-4.2, p = 0.03), vacuum extraction (Adjusted OR 7.01, 95% CI 3.5-14, p < 0.01), and forceps delivery (Adjusted OR 22.0, 95% CI 7.8-61, p < 0.01) were independently associated with fourth-degree perineal lacerations, while mediolateral episiotomy (Adjusted OR infinity, 95% CI 2.1-infinity, p = 0.03) and forceps delivery (Adjusted OR infinity, 95% CI 14.5-infinity, p = 0.01) were independently associated with rectovaginal fistulas. In addition, in the women with fourth-degree perineal lacerations, mediolateral episiotomy was associated with rectovaginal fistulas (OR infinity, 95% CI 1.8-infinity, p = 0.04).

CONCLUSIONS

Midline episiotomy and instrument-assisted delivery are independent risk factors for fourth-degree perineal lacerations after vaginal delivery. Mediolateral episiotomy and forceps delivery were independently associated with rectovaginal fistulas. Once fourth-degree perineal lacerations occurred, women with mediolateral episiotomies were more likely to develop rectovaginal fistulas.