Obstetric Anal Sphincter Injury: Interpregnancy Interval and Route of Subsequent Delivery.

Importance: Knowledge on the interpregnancy interval (IPI) among women with an obstetric anal sphincter injury (OASI) is both limited and not well understood.

Objectives: The objectives of this study were to describe the IPI among women with OASI and to compare women with OASI based on the route of subsequent obstetric delivery and OASI recurrence.

Study design: This was a retrospective single-cohort study of women who had an OASI between 2013 and 2015 at a tertiary academic medical center. Demographics, obstetric delivery data, postpartum sequelae, and subsequent pregnancy delivery data from 2013 to 2021 were collected. The IPI was defined as the time from date of first vaginal delivery to date of conception of the subsequent pregnancy. Women without a subsequent pregnancy were censored at the date of last contact. The IPI was evaluated using a survival analysis (Kaplan-Meier estimator).

Results: A total of 287 women experienced an OASI, and subsequent pregnancy occurred for 178 (62.0%) women. The median IPI was 26.4 months (95% confidence interval: 23.7-29.9) for women with a prior OASI. Of the 97 women who did not have a subsequent pregnancy documented during the study, the median follow-up was 64.0 months (interquartile range: 5.7-80.0). Subsequent delivery route data were available for 171 women; of those, 127 (74.3%) experienced a subsequent vaginal delivery and 44 (25.7%) experienced a cesarean delivery. Of the 127 women who experienced a subsequent vaginal delivery, 3 (2.4%) experienced a recurrent OASI.

Conclusion: The IPI among women with OASI is similar to the IPI for all women in Ohio and in the United States.