Pain Following Obstetric Anal Sphincter Injuries: A Prospective Cohort Study

Studies characterizing pain and pain management following obstetric anal sphincter injury (OASI) are limited.

Our primary objective was to analyze time to pain resolution following OASI. Secondary objectives included analyzing pain severity, location, triggers, and patterns of pain medication use.

This was a prospective cohort study of patients with OASIs seen in a postpartum care clinic at a tertiary referral center between 2017 and 2022. We analyzed data on pain resolution, visual analog scale pain scores, pain triggers, pain location, and pain medications.

A total of 362 patients were included in this study. In the Kaplan-Meier estimator, 58.5% of patients showed resolution of pain by 3 months following their initial postpartum care clinic visit, and 73.3% showed resolution of pain by 6 months. The median months to pain resolution was 2.2 (95% confidence interval: 1.6-3.0) for patients with third-degree lacerations and 2.3 (95% confidence interval: 1.6-6.8) for patients with fourth-degree lacerations. Visual analog scale scores showed the most improvement in the first 2 months. Common pain triggers included sitting and bowel movements in the first few months, as well as intercourse during later recovery. Pain location varied over time; bilateral pain in the levator ani muscles and obturator internus were most prevalent at each time point. Pain appeared to be predominantly managed by acetaminophen and ibuprofen.

Half of patients who experience OASI will have pain resolution by 2-3 months postpartum. Most patients will have resolution of their pain by 6 months postpartum.