Association between obstetrical anal sphincter injury and postpartum urinary retention: a contemporary nationwide cohort study.

Introduction And Hypothesis: Identification and prompt management of postpartum urinary retention after vaginal birth is essential to minimize long-term morbidity. Obstetrical anal sphincter injuries (OASIS) have been identified as a possible risk factor for urinary retention. The objective of this study was to estimate the association between OASIS and postpartum urinary retention and compare the length of hospital stay and cost of admission between postpartum patients who experienced urinary retention and those who did not.

Methods: We conducted a population-based, retrospective cohort study of pregnant individuals delivering singleton fetuses via vaginal birth in the United States using the National Inpatient Sample (NIS) database. Multivariate logistic regression models were used to estimate the odds ratio (OR) for the association between OASIS and postpartum urinary retention. Simple linear regression was used to compare means.

Results: A total of 2,013,052 delivery admissions were included, which was representative of a population size of 10,065,253 utilizing the complex sampling design of the NIS database. 47,192 (2.34%) admissions sustained OASIS and 5,339 (0.27%) admissions experienced overt urinary retention. After adjusting for potential confounders, vaginal deliveries where OASIS occurred had 3.60 times the odds of postpartum urinary retention compared with vaginal deliveries where OASIS was not sustained (95% CI 3.26-3.97). Postpartum urinary retention was associated with an increased mean length of stay (2.94 vs 2.28 days, p<0.001) and 1.37 times the mean total cost of admission (US$22,946.38 vs US$16,758.85, p<0.001).

Conclusions: Obstetrical anal sphincter injuries are associated with increased odds of postpartum urinary retention compared with vaginal deliveries where OASIS did not occur.