Complete Blood Count–Derived Inflammatory Indices for Early Prediction of Preterm Birth

Abstract

Preterm birth remains a major obstetric problem, and reliable early markers for identifying high-risk pregnancies are still limited. Inflammation-based indices obtained from routine complete blood count tests have recently been investigated as practical reflections of early immune activity. This study evaluates whether first-trimester hematologic inflammatory markers are associated with later spontaneous preterm birth. This study was conducted between 2023-2025. Pregnancies that ended before 37 weeks were compared with age-and sampling-matched term deliveries. Women with systemic disease, infections, multifetal gestation, fetal anomalies, or medication use influencing hematologic parameters were excluded. First-trimester inflammation-based indices were calculated. Statistical comparisons, correlation analyses, ROC curves, and logistic regression were performed. Among 426 participants, 142 experienced preterm birth. Those who later delivered preterm had higher neutrophil counts and elevated NLR, SII, and SIRI values compared with controls. NLR produced the highest discriminatory performance (AUC: 0.609), with a cut-off value of >2.832, yielding a sensitivity of 59.9% and a specificity of 60.9%. SII, SIRI, and AISI also demonstrated statistically significant but weaker predictive performance. Neonatal complications, including NICU admission, were more frequent in the preterm group. First-trimester inflammatory indices may signal early immune alterations related to preterm birth risk. Their predictive value alone is limited, yet they may strengthen early risk stratification when combined with established clinical parameters. Larger prospective studies are needed to confirm their additive contribution to predictive models.