Association between systemic immune-inflammation index and miscarriage: A case-control study

The systemic immune-inflammation index (SII), a novel biomarker of inflammation, has been proposed as a prognostic indicator. Recent studies have investigated its potential role in predicting pregnancy outcomes. However, findings have been inconsistent. The predictive value of SII for miscarriage remains unclear. This study aimed to evaluate the association between first-trimester SII levels and the risk of miscarriage. We conducted a retrospective study using data from the Third Affiliated Hospital of Wenzhou Medical University, covering the period from January to December 2022. Multivariable logistic regression analyses were employed to assess the relationship between SII and miscarriage. Additionally, interaction analyses were performed to explore the modifying effects of selected covariates. A total of 785 pregnancies were included in the analysis. In multivariable logistic regression models, when SII was treated as a continuous variable, a significant association with miscarriage was observed in Model III: for every 100-unit increase in SII, the odds of miscarriage increased. Compared with the low SII group, those with high SII levels (≥1296.2) had a significantly increased risk of miscarriage (OR: 1.75; 95 % CI: 1.12-2.74). Subgroup analyses revealed no significant interactions when stratified by age, history of miscarriage, or history of full-term birth. However, an interaction was observed between first-trimester SII and body mass index. Our findings indicate a significant association between elevated first-trimester SII levels and an increased risk of miscarriage.