Maternal outcomes in subsequent delivery after previous obstetric anal sphincter injury (OASI): a multi-centre retrospective cohort study

Int Urogynecol J. 2020 Mar;31(3):627-633. doi: 10.1007/s00192-019-03983-0. Epub 2019 Jun 22.


Introduction and hypothesis: Women with a history of obstetric anal sphincter injury (OASI) are at increased risk of recurrence (rOASI) at subsequent delivery; however, evidence regarding the factors influencing this risk is limited. Furthermore, little is known about what factors influence the decision to alternatively deliver by elective caesarean section (ELLSCS).

Methods: Retrospective univariate and multivariate logistic regression analysis of prospectively collected data from four NHS electronic maternity databases including primiparous women sustaining OASIS during a singleton, term, cephalic, vaginal delivery between 2004 and 2015, who had a subsequent delivery.

Results: Two thousand two hundred seventy-two women met the criteria; 10.2% delivering vaginally had a repeat OASI and 59.4% had a second-degree tear. Women having an ELLSCS were more likely to be Caucasian, older, have previously had an operative vaginal delivery (OVD) and have a more severe degree of OASI. Positive predictors for rOASI were increased birth weight and maternal age at both index and subsequent deliveries, a more severe degree of initial OASI and Asian ethnicity. The overall mediolateral episiotomy (MLE) rate was 15.6%; 77.2% of those who had an episiotomy sustained no spontaneous perineal trauma. Only 4.4% of women with a rOASI had an MLE, whilst the MLE rate was 16.9% in those without a recurrence (p < 0.001). MLE decreased the risk of rOASI by 80%. Birth weight > 4 kg increased the risk 2.5 fold.

Conclusions: Women with previous OASIS are at an increased risk of recurrence. A more liberal use of MLE during subsequent vaginal delivery could significantly reduce the risk of recurrence.

Keywords: Mediolateral episiotomy; Obstetric anal sphincter injuries; Perineal trauma; Recurrent obstetric anal sphincter injury.

MeSH terms

  • Anal Canal*
  • Cesarean Section / adverse effects
  • Delivery, Obstetric / adverse effects
  • Episiotomy / adverse effects
  • Female
  • Humans
  • Obstetric Labor Complications* / epidemiology
  • Obstetric Labor Complications* / etiology
  • Pregnancy
  • Retrospective Studies
  • Risk Factors