Obstetric anal sphincter injury after episiotomy in vacuum extraction: an epidemiological study using an emulated randomised trial approach. Academic Article uri icon

abstract

  • OBJECTIVE: To emulate a randomised controlled trial investigating whether lateral or mediolateral episiotomy compared with no episiotomy reduces the prevalence of obstetric anal sphincter injury (OASIS) in nulliparous women delivered with vacuum extraction. DESIGN: A population-based observational study. SETTING: Sweden. POPULATION: 63654 nulliparous women delivered with vacuum extraction derived from the Swedish Medical Birth Register 2000-2011, with a live singleton baby with no known malformations in cephalic presentation in gestational week34+0 , and subject to lateral or mediolateral episiotomy or no episiotomy. METHODS: The effect of episiotomy was calculated using a causal doubly robust estimation method based on propensity scores. Results are presented as the average treatment effect and numbers needed to treat (NNT). MAIN OUTCOME MEASURES: OASIS (third- and fourth-degree perineal injury) in nulliparous women delivered with vacuum extraction. RESULTS: Episiotomy was associated with a reduction in OASIS from 15.5% to 11.8%, average treatment effectof -3.66% (95% CI-4.31 to-3.01) and NNT 27. Third-degree perineal injuries were reduced from 14.0% to 10.9% (-3.08, 95% CI-3.71 to-2.42) with NNT 32. Fourth-degree perineal injuries were reduced from 1.6% to 1.0 % (-0.58%, 95% CI-0.79 to-0.37) with NNT 172. CONCLUSIONS: Lateral or mediolateral episiotomy reduced the prevalence of OASIS in nulliparous women delivered with vacuum extraction, compared to women with no episiotomy. TWEETABLE ABSTRACT: To prevent one case of OASIS in first-time mothers delivered with vacuum, 27 episiotomies had to be performed.

published proceedings

  • BJOG

altmetric score

  • 10.4

author list (cited authors)

  • Ankarcrona, V., Zhao, H., Jacobsson, B., & Brismar Wendel, S.

citation count

  • 7

complete list of authors

  • Ankarcrona, V||Zhao, H||Jacobsson, B||Brismar Wendel, S

publication date

  • September 2021

publisher