Risks and Associations of Third- and Fourth-Degree Lacerations: An Urban Single Center Experience

Obstetric anal sphincter injuries (OASIs) are severe tears involving the external and internal anal sphincters. We aimed to document the incidence of OASIs within a racially and ethnically diverse institution to elucidate which maternal, fetal, and parturition factors may be associated with OASIs in minority subgroups.

This was a retrospective unmatched case-control study of reproductive aged women who delivered between January 1, 2014, and December 31, 2017, at our institution. Data for maternal, fetal, and parturition factors were gathered through chart review. We also investigated the expertise level of the surgeon performing repairs and complications that developed in the postpartum period. Logistic regression analysis was used to compare women with third- and fourth-degree lacerations against the control group of women with first-degree, second-degree, or no lacerations.

Of the 23,362 deliveries between January 1, 2014, and December 31, 2017, the incidence of OASIs was 1%. Of our patients, 38% self-identified as Hispanic, 32% as Black, 13% as White, and 3.5% as Asian. Risk for OASIs was significantly increased in nulliparity, Pitocin use, operative deliveries, episiotomy, and prolonged second stage of labor. Black race and obesity were protective for OASIs. There was no significant difference in complication rates based on type of repair nor the provider level of training.

The incidence of OASIs at our institution is similar to current published literature. Our study population is unique in its overrepresentation of minority groups, offering insight into potentially distinctive risk and protective factors associated with OASIs.