Association Between the Systemic Immune Inflammation Index and Systemic Inflammatory Response Index with Gestational Diabetes Mellitus and Preeclampsia: A Systematic Review and Meta-Analysis

Systemic inflammation plays a key role in the pathophysiology of pre-eclampsia (PE) and gestational diabetes mellitus (GDM). Recently, the Systemic Immune Inflammation (SII) and Systemic Inflammation Response Index (SIRI) indices have emerged as potential risk predictors, but current evidence shows mixed results. The aim of this meta-analysis was to assess the association between elevated SII/SIRI levels and the development of both complications. In accordance with the PRISMA guidelines, a search was conducted in PubMed, Scopus and Web of Science (up to February 2026). Observational studies linking the SII and SIRI indices to PE and GDM were included. Methodological quality (NHLBI tools) and evidence (GRADE) were assessed, and a random-effects meta-analysis was applied to synthesise the measures of association. Thirteen studies involving more than 150,000 pregnant women were included. The meta-analyses demonstrated that elevated levels of SII and SIRI are associated with an increased risk of GDM by 28% (OR = 1.28; 95% CI: 1.16–1.42) and 27% (OR = 1.27; 95% CI: 1.11–1.48) respectively, albeit with considerable heterogeneity. They also increase the risk of PE by 16% (OR = 1.16; 95% CI: 1.08–1.24) and 21% (OR = 1.21; 95% CI: 1.05–1.40), without significant heterogeneity. Although the quality of the studies was good, the strength of the evidence was low for GDM and very low for PE. Therefore, while these indices show potential as early biomarkers, these findings should be considered suggestive and require further validation and standardisation across diverse populations.