Risk factors for obstetric anal sphincter injuries during vaginal delivery: can we reduce the burden?

Background: Third- and fourth-degree perineal tears are associated with significant discomfort and impact on women's quality of life after labor. We reviewed the literature on risk factors for obstetric anal sphincter injuries (OASIS), focusing on modifiable risk factors for OASIS to help obstetricians prevent them. Methods: We searched Cochrane Database of Systematic Reviews, and Scopus using key search terms. We selected clinical studies, systematic reviews, and meta-analyses in English investigating antepartum and intrapartum factors associated with OASIS. Three researchers independently selected studies and documented outcomes. Results: We identified forty-two relevant articles for inclusion. Among antepartum factors, primiparity, neonatal birth weight, and ethnicity were associated with a higher risk of OASIS. Instrumental delivery, midline episiotomy, duration of the second stage of labor, persistent occiput posterior position, and labor augmentation were those intrapartum factors reported associated with OASIS. Conclusions: Multiple anteand intrapartum factors are associated with a higher risk of OASIS. The actual modifiable factor is episiotomy during the second stage of labor. However, literature reporting episiotomy associated with a reduction in OASIS prevalence during instrumental delivery is limited. gation on the role of episiotomy in an operative delivery.