Association Between Systemic Inflammatory Response Index at Labour Admission and Episiotomy Wound Dehiscence After Vaginal Delivery.

Background/Objectives: We examined the association between the systemic inflammatory response index (SIRI) measured on admission in labour and complete episiotomy wound dehiscence, and whether the SIRI adds useful discrimination beyond available covariates. Methods: This retrospective case-control study included 200 cases and 200 controls attending postpartum clinics at a tertiary maternity unit (September 2019-September 2022). Controls were randomly sampled from eligible attendees on the same clinic days. The SIRI was calculated from pre-delivery blood counts. Unconditional logistic regression adjusted for maternal age, primiparity, education, income, birthweight and gestational age. Important intrapartum and repair variables were unavailable. Results: The median SIRI was 3.00 in cases and 2.52 in controls (p < 0.001). The log-transformed SIRI was associated with dehiscence after adjustment (OR 1.49 per doubling, 95% CI 1.13-1.97; p = 0.005), whereas the untransformed term was not statistically significant (p = 0.063). The SIRI had poor discrimination (AUC 0.601, 95% CI 0.544-0.655). Adding the SIRI increased the reference-model AUC from 0.699 to 0.713 (ΔAUC 0.014, 95% CI 0.001-0.039); adding neutrophil count yielded an AUC of 0.712. Conclusions: In this selected clinic-attending population, the SIRI showed a model-dependent association with dehiscence but insufficient discrimination for individual risk prediction. Residual confounding remains possible. The small incremental gain does not support using the SIRI for clinical risk stratification or treatment decisions.