Utility of maternal A1c measurement in the second trimester for the diagnosis of gestational diabetes mellitus

Background To investigate the effectiveness of maternal hemoglobin A1c (HbA1c) in the diagnosis of gestational diabetes mellitus (GDM) in the second trimester. Methods A total of 3000 pregnant women between 24 and 28 weeks of gestation were included in the study. Screening for gestational diabetes was performed using maternal HbA1c in 1200 pregnant women who either refused or could not tolerate the OGTT. The HbA1c value for the diagnosis of GDM was set at >= 5.7% in accordance with a meta-analysis by Paula B. Renz et al. A total of 154 pregnant women with HbA1c >= 5.7% were diagnosed with gestational diabetes, and their data were recorded prospectively. These data were compared with obstetric outcomes in 250 pregnant women diagnosed with diabetes by performing a 100-g OGTT after a 50-g glucose challenge test (GCT). Results There were no significant differences between two groups in terms of maternal age, gestational age at diagnosis, gravidity, and parity. Body mass index (BMI) was found to be significantly higher in pregnant women with HbA1c levels >= 5.7% (p < 0.001). Polyhydramnios was more common in the HbA1c >= 5.7% group and oligohydramnios was more common in the OGTT group (p < 0.001). Neonatal hypoglycemia was found to be significantly higher in the OGTT group (p < 0.05). The median HbA1c value were different in each group (OGTT group 5.6%, HbA1c group 5.8%; p < 0.001). Conclusion HbA1c testing has lower accuracy rates than OGTT in diagnosing GDM because it may miss diagnosis in some groups.