Usefulness of HbA1C in differentiating Gestational Diabetes Mellitus and preexisting Diabetes Mellitus in the early stages of pregnancy

Introduction: Diabetes mellitus in pregnancy can cause several complications for the mother and the neonate if left untreated. This study identifies the proportion of undiagnosed pre-existing diabetic pregnant women and the necessity of doing an HbA1C test in the first trimester for its diagnosis.Methodology: Pregnant women in the first trimester without a history of hypertensive disorders, Diabetes Mellitus in their previous pregnancies were recruited for the studies. Then blood samples were withdrawn from them to perform OGTT and the HbA1C test on booking visit (8-12 weeks of gestation). The results were used to diagnose and find the proportions of pregnant women with pre-existing diabetes mellitus and gestational diabetes mellitus.Results: The HbA1C test was done for 428 pregnant women and among them, 25 (5.8%) had levels above ≥ 48 mmol/mol (6.5%) and were diagnosed with pre-existing diabetes. Of the 428 pregnant women, only 267 attended the OGTT. Among the 267 pregnant women, 15 had HbA1C levels equal to or more than 6.5% and they were identified to have pre-existing diabetes. Pregnant women diagnosed with gestational diabetes were 34 and the HbA1C of these women was <6.5%. However, the 15 pregnant women who were diagnosed with preexisting diabetes were not identified with gestational diabetes from the OGTT.Conclusion: HbA1C can be used as a useful tool for screening pre-existing diabetes during pregnancy. Due to the high prevalence of pregnant women with pre-existing diabetes (5.8%) found in this study, it can be recommended to perform a HbA1C test at the booking visit to identify high-risk, pregnant women.