Evaluation of Systemic Inflammatory Indices in Pregnant Women With Deep Vein Thrombosis

Abstract

Objective Venous thromboembolism (VTE) remains an important cause of maternal morbidity and mortality, yet the diagnosis of deep vein thrombosis (DVT) during pregnancy is challenging because clinical symptoms overlap with physiological gestational changes and D-dimer specificity is reduced. This study evaluated the association between complete blood count-derived systemic inflammatory indices and pregnancy-associated DVT.Methods This retrospective case-control study included 36 pregnant women with Doppler ultrasonography-confirmed DVT and 36 healthy pregnant controls matched for maternal age and gestational age. 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 aggregate index of systemic inflammation (AISI) were calculated from routine complete blood counts. Univariable and multivariable Firth penalized logistic regression analyses were performed, adjusting for body mass index, history of cesarean delivery, and varicose veins. Elastic net penalized regression was used for variable selection. Gestational age-stratified sensitivity analyses, false discovery rate correction, receiver operating characteristic (ROC) analyses, and a supplementary trimester-specific D-dimer threshold analysis were also performed.Results Women with DVT had higher NLR, SII, SIRI, AISI, and D-dimer levels than controls, whereas PLR and MLR did not differ significantly. After false discovery rate correction, NLR, SII, SIRI, and AISI remained statistically significant. In multivariable Firth regression, NLR, SII, and D-dimer were independently associated with DVT. Elastic net analysis identified NLR and SII as the most informative inflammatory indices. ROC analyses showed moderate discriminatory performance for NLR and SII, either alone or combined with D-dimer. The gestational age-stratified analyses showed a consistent direction of association, while trimester-specific D-dimer thresholds increased specificity but substantially reduced sensitivity in this cohort.Conclusion NLR and SII were associated with pregnancy-associated DVT and may reflect the thrombo-inflammatory component of this condition. However, the findings are exploratory and hypothesis-generating. These indices should be considered only as adjunctive markers within the existing diagnostic workflow, not as standalone diagnostic tools. Prospective studies using standardized sampling and pregnancy-adapted D-dimer strategies are needed before clinical implementation.