Predictive Accuracy of First-Trimester Biochemical and Clinical Markers in the Early Identification of Gestational Diabetes Mellitus: A Prospective Observational Study.

Background Gestational diabetes mellitus (GDM) is a common metabolic complication of pregnancy associated with significant maternal and fetal morbidity. Early identification of women at risk is essential to improve outcomes. This study evaluated the predictive accuracy of first-trimester biochemical and clinical markers for the early detection of GDM in a South Indian population. Methods A prospective observational study was conducted at a tertiary care hospital in South India over eight months. A total of 118 antenatal women between 11 and 14 weeks of gestation were enrolled. All participants underwent assessment of serum C-reactive protein (CRP), uric acid, and postprandial blood sugar (PPBS) levels, along with clinical evaluation of body mass index (BMI), history of polycystic ovary syndrome (PCOS), and family history of diabetes mellitus. Between 24 and 28 weeks, all women underwent a 75-gram oral glucose challenge test as per the Diabetes in Pregnancy Study Group India (DIPSI) criteria. GDM was diagnosed if the two-hour plasma glucose was ≥140 mg/dL. Statistical analysis included receiver operating characteristic (ROC) curve analysis, logistic regression, and correlation studies. Results The incidence of GDM was 27.9% (31/118). Mean CRP, uric acid, and PPBS levels in the first trimester were significantly higher in the GDM group (CRP: 12.96 ± 5.38 mg/L vs. 5.51 ± 3.12 mg/L; uric acid: 3.31 ± 0.52 mg/dL vs. 3.02 ± 0.28 mg/dL; PPBS: 133.06 ± 13.15 mg/dL vs. 92.56 ± 5.57 mg/dL; all p<0.05). ROC analysis showed high predictive accuracy for CRP (area under the curve (AUC) = 0.94, cut-off >8.5 mg/L) and PPBS (AUC = 0.85, cut-off >110 mg/dL). Logistic regression identified CRP (OR: 6.21), PPBS (OR: 4.76), history of PCOS (OR: 3.66), and family history of diabetes (OR: 3.45) as independent predictors of GDM. Among the evaluated biomarkers, CRP (>8.5 mg/L) showed the highest diagnostic accuracy with a sensitivity of 83.9% and specificity of 87.4%, followed by PPBS (>130 mg/dL) with a sensitivity of 80.6% and specificity of 85.1%, while uric acid (3.3 mg/dL) demonstrated comparatively lower diagnostic performance. A combined model of CRP, PPBS, and clinical risk factors achieved excellent predictive value (R² = 0.79). Conclusion First-trimester CRP and PPBS, alongside PCOS and family history, were associated with DIPSI-defined GDM in a single-centre cohort; uric acid was not independently predictive. These preliminary results require multicentre external validation and clinical-utility assessment before any screening or management recommendations can be made. Larger, multicentric studies are warranted to confirm these findings and to support the integration of multifactorial risk-based screening into routine antenatal care.