Racial/Ethnic Impact on Obstetric Anal Sphincter Injuries: A Multicentric Retrospective Study

Introduction and hypothesis: Obstetric anal sphincter injuries (OASIs), third- and fourth-degree lacerations, represent a severe obstetric complication. Previous studies reported a higher incidence of OASIs in Asian women in non-Asian countries. This study was aimed at establishing a different OASIs prevalence among the racial/ethnic groups in Southern European centers. Methods: A multicenter retrospective study that included pregnant women who had vaginal singleton delivery between January 2019 and September 2022 in two Italian University hospitals, Naples and Novara, was conducted. We excluded cesarean sections, nonvertex presentation, preterm delivery, multiple pregnancies, congenital malformations, or stillbirths. Statistical analysis with an independent association of ethnicity to the risk of OASIs using clinical characteristics-adjusted multivariate logistic regression was performed. Results: A total of 3,049 pregnant women were included. 2.33% (71 patients) had an OASI. The median age was 31 years (IQR 7.00) and median gestational age was 39 weeks (IQR 1.40). Mean birth weight was 3,300 g (IQR 580.00). 1' and 5' Apgar scores were 9 and 9. The univariate logistic regression was not statistically significant. Multivariate logistic regression model adjusted for baseline clinical characteristics showed an OR 2.540 (p value 0.01) for OASIs in Asian women. Primiparous and secondiparous were protective factors for OASIs with OR 0.224 (p value < 0.001) and OR 0.209 (p value 0.01). Conclusions: Our results confirm racial/ethnic disparities regarding OASIs, with an elevated risk for Asian women in Southern Europe. Prevention strategies and obstetric care in developed countries should be modulated to offset the risk of OASIs in this population. Additional research is needed to explain the specific mechanisms of these disparities.