TOPLINE

Mediolateral episiotomy is associated with a 40%-46% reduction in obstetric anal sphincter injury (OASI) risk for patients without previous vaginal delivery undergoing operative vaginal delivery (OVD). In contrast, midline episiotomy more than doubles the risk for OASI in vacuum-assisted vaginal delivery and quadruples it in patients with prior vaginal delivery.

METHODOLOGY

• Researchers conducted a secondary analysis of 5277 patients who had OVD of a term, cephalic singleton neonate in the Maternal-Fetal Medicine Units Network's Assessment of Perinatal Excellence (APEX) cohort at 25 designated hospitals throughout 14 clinical centers in the United States between March 2008 and February 2011. 
• Among participants, 3453 had vacuum-assisted vaginal delivery and 1824 had forceps-assisted vaginal delivery; episiotomy was performed in 1704 deliveries (32.3%), including 1301 midline, 384 mediolateral, and 19 of unknown type. 
• Multivariable logistic regression adjusted for length of the second stage of labor (< 1 hour, 1 to < 2 hours, ≥ 2 hours), maternal age (< 20 years, 20-24 years, 25-29 years, 30-34 years, ≥ 35 years), BMI (< 25, 25-29.9, 30-34.5, 35-39.9, ≥ 40), and birth weight (continuous). 
• Researchers tested for interaction in the association between episiotomy type and OASI by OVD type (vacuum-assisted vaginal delivery vs forceps-assisted vaginal delivery) and vaginal delivery history (no prior vaginal delivery vs prior vaginal delivery). 
• The primary outcome was OASI, defined as a third-degree or fourth-degree perineal laceration, and the exposure was episiotomy (midline or mediolateral). 

TAKEAWAY

• Overall incidence of OASI was 20.1% (95% CI, 19.0%-21.2%); adjusted odds of OASI were higher in patients with episiotomy compared with those without episiotomy (adjusted odds ratio [aOR], 1.45; 95% CI, 1.25-1.67). 
• In patients without previous vaginal delivery who delivered with forceps, mediolateral episiotomy compared with no episiotomy was associated with lower odds of OASI (aOR, 0.54; 95% CI, 0.35-0.83), whereas midline episiotomy was not significantly associated with OASI (aOR, 0.90; 95% CI, 0.69-1.18). 
• Among patients without previous vaginal delivery who delivered with vacuum, mediolateral episiotomy compared with no episiotomy was associated with lower odds of OASI (aOR, 0.60; 95% CI, 0.38-0.96), whereas midline episiotomy was associated with higher odds of OASI (aOR, 2.24; 95% CI, 1.81-2.77). 
• Among patients with previous vaginal delivery who delivered with vacuum, midline episiotomy compared with no episiotomy was associated with higher odds of OASI (aOR, 4.06; 95% CI, 2.54-6.50); the protective association of mediolateral episiotomy was retained only in patients with BMIs less than 30 (aOR, 0.43; 95% CI, 0.28-0.65). 

IN PRACTICE

"Mediolateral episiotomy was associated with lower odds of obstetric anal sphincter injury for patients without previous vaginal delivery undergoing OVD. In contrast, midline episiotomy was associated with increased odds of obstetric anal sphincter injury for vacuum-assisted vaginal delivery regardless of vaginal delivery history," wrote the authors of the study.

SOURCE

The study was led by Alexis A. Doyle, MD, MSc, University of Utah Health, Salt Lake City. It was published online in Obstetrics & Gynecology.

LIMITATIONS

The database lacked granularity regarding episiotomy angle, length, and operator experience, all of which can influence OASI outcomes. If a portion of mediolateral episiotomies were actually midline, this would potentially underestimate the protective effect of mediolateral episiotomy. The database did not include information about other important components of OASI prevention, including manual perineal support, warm compresses, and perineal massage. As a retrospective study, the timing and decision-making surrounding need for episiotomy were unknown. Regional and hospital-specific differences in practices surrounding episiotomy and OVD could not be adjusted for, because hospital site was not available in the deidentified data release. As a secondary analysis, the results should be interpreted as hypothesis generating. Some analyses have a small number of patients with the outcome, resulting in wide CIs reflecting uncertainty in the point estimates. There are no data from the APEX cohort on the short- and long-term maternal outcomes after episiotomy.

DISCLOSURES

The authors acknowledged assistance from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Maternal-Fetal Medicine Units Network, and the APEX Protocol Subcommittee in making the database available for this research. Torri D. Metz served as the site principal investigator for a Pfizer study of Paxlovid in pregnancy, a Moderna study of respiratory syncytial virus (RSV) vaccination in pregnancy, and a Pfizer study of RSV vaccination in pregnancy. She disclosed receiving UpToDate royalties for two topics on trial of labor after cesarean. The remaining authors reported no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.