(1013) Episiotomy and Anal Sphincter Injury during Operative Vaginal Delivery in a United States Cohort

Objective:
To assess the association between episiotomy and obstetric anal sphincter injury (OASI) during operative vaginal delivery (OVD) in a diverse, modern U.S. cohort.

Study Design:
Secondary analysis of patients who had an OVD of a term, cephalic singleton in the MFMU APEX cohort. The primary outcome was OASI (3rd or 4th degree laceration). The exposure was episiotomy. Multivariable logistic regression adjusted for length of 2nd stage, age, BMI, and birth weight. We tested for interactions between episiotomy and laceration by OVD type, history of vaginal delivery, and episiotomy type.

Results:
Among 5277 participants, 3453 had a vacuum-assisted vaginal delivery (VAVD) and 1824 had forceps (FAVD) (Table). An episiotomy was performed in 1704 (32%) of the deliveries (n=1301 midline, n=384 mediolateral, n=19 unknown type). The OASI incidence was 20.1% (95% CI 19.0-21.2). Overall, the odds of OASI were higher among patients with an episiotomy (aOR: 1.45, 95%CI:1.25-1.67). There was a significant interaction between episiotomy and laceration by instrument type (p< 0.001), history of vaginal delivery (p=0.02) and episiotomy type (p< 0.001) prompting a stratified analysis by these subgroups. In a multivariable model, compared with no episiotomy, midline episiotomy during a VAVD was associated with higher odds of OASI for patients both with or without a prior vaginal delivery. In contrast, mediolateral episiotomy was associated with lower odds of OASI for patients with no prior vaginal delivery for both VAVD and FAVD (Figure). No other subgroups significantly differed from no episiotomy in association with OASI.

Conclusion:
Mediolateral episiotomy was associated with lower odds of OASI for patients undergoing OVD without a history of vaginal delivery. In contrast, episiotomy was not associated with a difference in OASI for patients with a prior vaginal delivery. These findings are consistent with several previous studies conducted in settings with different baseline rates of OVD and episiotomies and indicate there may be a subgroup of patients who could benefit from mediolateral episiotomy prior to OVD.