STUDY TO DETERMINE DIAGNOSTIC ACCURACY OF FIRST TRIMESTER GLYCOSYLATED HAEMOGLOBIN FOR PREDICTION OF GESTATIONAL DIABETES MELLITUS

Gestational Diabetes Mellitus (GDM) is a rising public health concern, particularly in South Asian populations with inherent insulin resistance. Early identification of high-risk pregnancies is critical to minimize maternal and fetal complications. Glycosylated hemoglobin (HbA1c), a marker of average blood glucose over 2–3 months, may offer a convenient early screening option when measured in the first trimester. Objective:This study aimed to evaluate the diagnostic accuracy of first-trimester HbA1c in predicting GDM and to determine an optimal HbA1c cutoff that could serve as a risk stratification tool in routine antenatal care. Methods:A prospective cohort study was conducted at a tertiary care hospital over six months. A total of 100 pregnant women with gestational age 8–13 weeks were enrolled. First-trimester HbA1c was measured using high-performance liquid chromatography. All participants underwent a 75 g OGTT at 24–28 weeks, and GDM was diagnosed as per IADPSG criteria. Data were analyzed using SPSS, and the diagnostic accuracy of HbA1c was assessed through sensitivity, specificity, and ROC analysis. Results:GDM was diagnosed in 15% of participants. All GDM cases had a first-trimester HbA1c ≥ 5.7%, showing 100% specificity but reduced sensitivity. A significant association was observed between GDM and obesity (p < 0.001), with all cases occurring in obese women. HbA1c ≥ 5.7% demonstrated strong predictive value but cannot replace OGTT due to limited negative predictive capacity. Conclusion:First-trimester HbA1c ≥5.7% is a useful high-specificity screening tool for GDM but lacks sufficient sensitivity to serve as a standalone diagnostic test. When combined with mid-pregnancy OGTT, it enhances early detection and facilitates targeted interventions.