Trends in obstetric anal sphincter injury in spontaneous vaginal delivery versus operative vaginal delivery over a 10‐year period: Lessons learned

Objective To evaluate trends in the incidence of women with obstetric anal sphincter injuries (OASIS) over a 10‐year period comparing spontaneous vaginal delivery (SVD) and operative vaginal delivery (OVD). Methods A retrospective study was performed in which all women who underwent vaginal delivery over a 10‐year period ( n = 86 242, 2009–2018) at the Rotunda Hospital were reviewed. The overall incidence of OASIS was compared with incidence rates stratified by parity and type of vaginal birth. Results The 10‐year vaginal delivery rate was 69% ( n = 59 187) where 24 580 women (42%) were primiparous and 34 607 women (58%) were multiparous. SVD rate was 74% and OVD rate was 26%. The overall incidence of OASIS was 2.9%. The incidence of OASIS in OVD was 5.5% and the incidence in SVD was 2%. Of 498 multipara who sustained OASIS, 366 (73%) had an SVD without episiotomy compared with 14 (3%) who had an episiotomy. There was a significant reduction of OASIS over the 10‐year period in primipara who had an OVD but no reduction in the other groups. Conclusion The primiparous OVD group had a significant reduction of OASIS. Continued education around perineal protection and episiotomy at SVD could positively impact further reduction in OASIS, particularly in the SVD groups.