Residents’ Exposure to OASIS: Temporal Trends over 16-Years

Objectives: To quantify residents’ exposure to obstetric anal sphincter injuries (OASIS) and repair during a 4-year obstetrics and gynecology (OBGYN) residency and examine trends over a 16-year period.

Methods: A retrospective cohort study of individuals who sustained an OASIS (3rd or 4th degree laceration) during vaginal delivery (VD) at a single academic hospital system from 2007-2022. Individuals who sustained an OASIS during spontaneous vaginal delivery (SVD) or operative vaginal delivery (OVD) with the use of forceps or vacuum were included. Individuals were identified by ICD-9 (2007-2014) and ICD-10 codes (2015-2002). Institutional rates of SVD, OVD, and cesarean delivery (CD) were also examined. Four-year epoch were used to examine temporal trends in OASIS over time and determine average resident exposure during OBGYN residency. Basic descriptive statistics were used to examine differences in continuous variables, and Pearson’s χ2 test was used for categorical variables where appropriate. Statistical analyses were performed using SAS 9.4 (Cary, NC).

Results: During the 16-year study period, there were 103,234 deliveries with 62% VD, 4% OVD, and 34% CD (Table 1). Among VD, 2344 (3%) sustained an OASIS with 2075 (89%) being 3rd degree lacerations and 269 (12%) 4th degree lacerations. While 1725 (74%) of OASIS occurred following SVD, 619 (26%) occurred following OVD. Rate of OASIS after SVD decreased over the study period from 3.6% to 2.2%, p < 0.001 whereas OASIS after OVD increased over time (12.0% to 14.4%), p < 0.001. The number of residents increased by 47% (17 in 2007-2011 to 25 in 2018-2022). Resident exposure to OASIS during a 4-year OBGYN residency decreased over the study period: 45 in 2007-2010, 27 in 2011-2014, 22 in 2015-2018, and 20 in 2019-2022. Average resident exposure to 3rd and 4th degree lacerations decreased over the study period (3rd degree: 38 to 18; 4th degree: 6 to 2; Figure 1). Average resident exposure to OVD and CD also decreased over the study period from 82 to 38 OVD and from 574 to 327 CD. For every single 4th degree laceration, the average resident performed 164 CD.

Conclusions: At our center, during their 4-years of training, an average resident was exposed to two 4th degree lacerations and fewer than 20 3rd degree lacerations. The infrequent exposure to evaluation and management of OASIS is concerning as surgical management of OASIS is an essential obstetric procedure and core competency in the ACGME residency curriculum. Supplementation with simulation is necessary to train competent surgeons in management of OASIS.