Systematic Review of Association Between Race & Obstetric Anal Sphincter Injury

Objectives: Our primary aim was to conduct a systematic review and meta-analysis to examine the association between race and incidence of obstetric anal sphincter injuries (OASIS). The secondary aim was to critique the included studies on how they contextualized race as a risk factor for OASIS.

Methods: We searched MEDLINE, EMBASE, Cochrane, and Web of Science databases for observational studies with vaginal deliveries reporting incidence of OASIS by race since 2012. The primary outcome was the pooled OASIS incidence and pooled odds ratio (OR) for OASIS by race using a random effect model. We also performed meta-regression analysis to examine OASIS incidence by geographic (national vs regional) and time-period (earlier data from 2000s vs after) variations for each racial group. To evaluate the generalizability of our findings, we analyzed each racial group’s representation in the studies relative to their respective demographics based on US census data using a representation quotient analysis (RQ), with underrepresentation defined as RQ < 1. Finally, we used questions from sections of the Obstetrics & Gynecology’s Equity Rubric to perform a structured critique of how the included studies used race as a variable in their investigation and interpretation.

Results: We identified 3,896 studies, of which 12 studies with over 39 million vaginal deliveries were included. The overall OASIS incidence was 4.44% (95% CI, 2.69%-6.60%) with Asian individuals having the highest (5.69%; 95% CI, 4.04%-7.59%). There was no association based on geographic or temporal variations for all racial groups. When compared to White individuals, Asian individuals had higher odds of OASIS (OR 1.61; 95% CI, 1.12-2.31) while Black and Hispanic individual had lower odds (OR 0.47; 95% CI, 0.38-0.57 and OR 0.63; 95% CI, 0.63-0.64, respectively). We found significant data underrepresentation among Black (RQ 0.15) and Hispanic (RQ 0.20) individuals. Our results did not differ significantly after performing sensitivity analyses by excluding studies with potentially overlapping populations or those with high risk of bias.

When critiquing the 12 included studies with the Equity Rubric, no study was explicit about how their research may improve health outcomes for the included marginalized racial populations. Of the 9 studies that identified racial disparity in OASIS incidence, 33% attributed the findings to systemic factors, 45% did not comment on the disparity, and 22% claimed biological differences without citation of relevant evidence. Of the 3 studies that did not identify racial disparity, 2 were due to smaller sample sizes but 1 was due to aggregation of Asian individuals as “others” without a clear explanation.

Conclusions: Asian individuals were 61% more likely to experience OASIS than their White counterparts. However, this disparity was not acknowledged in most studies. There is a critical need to understand structural factors that perpetuate maternal pelvic floor injuries disparity among Asian American individuals.