Association of Early Pregnancy Inflammatory Indices with Preterm Birth and Perinatal Outcomes in Pregnancies with Pregestational Diabetes

<b>Background/Objectives:</b> We aimed to investigate the relationship between early pregnancy inflammatory indices and adverse perinatal outcomes in pregnancies complicated by pregestational diabetes mellitus (PREGDM) and to evaluate their predictive value, particularly for preterm birth and composite adverse perinatal outcome (CAPO). <b>Methods:</b> This retrospective study included 140 women with PREGDM and 140 age-matched controls. Early pregnancy (8-14 weeks) inflammatory indices [the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI)], and C-reactive protein (CRP) were calculated from complete blood counts. Associations with preterm birth and CAPO were analyzed using correlation, ROC analysis, and multivariate logistic regression adjusted for maternal age, BMI, HbA1c, and parity. <b>Results:</b> All inflammatory indices were significantly higher in the PREGDM group compared to controls (<i>p</i> < 0.05). Preterm birth, macrosomia, cesarean delivery, NICU admission, and CAPO were more frequent in PREGDM pregnancies (all <i>p</i> < 0.001). On univariate analysis, NLR, PLR, MLR, SII, and SIRI were significantly higher in women with preterm birth (<i>p</i> < 0.05), but not in those with CAPO. ROC curves showed modest discriminative ability of NLR, PLR, and SII for preterm birth (AUC 0.64-0.66), while AUCs for CAPO prediction were close to 0.5. In multivariate analysis, inflammatory indices were not independent predictors of either outcome. Only HbA1c (OR: 1.71, 95% CI 1.20-2.43, <i>p</i> = 0.003) and parity (OR: 1.62, 95% CI 1.08-2.45, <i>p</i> = 0.021) independently predicted preterm birth, and similarly HbA1c (OR: 1.68, 95% CI 1.14-2.46, <i>p</i> = 0.008) and parity (OR: 1.49, 95% CI 1.02-2.15, <i>p</i> = 0.037) predicted CAPO. <b>Conclusions:</b> Early pregnancy inflammatory indices were associated with preterm birth in univariate analyses but lost significance after adjustment for maternal and metabolic risk factors. HbA1c and parity remained the only independent predictors of adverse outcomes in PREGDM pregnancies. Inflammatory indices may provide supplementary information but should not be used as stand-alone predictors; they may instead be incorporated into multiparametric models with established clinical and metabolic markers to improve risk stratification.