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

Background: The aim of this study was to investigate the impact of changes in diagnostic processes and criteria for gestational diabetes mellitus (GDM) on adverse obstetric outcomes associated with GDM. 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 hemoglobin A1c (HbA1c) in 1200 pregnant women who either refused or could not tolerate the oral glucose tolerance test (OGTT). The HbA1c cut-off value for the diagnosis of GDM was set at ≥5.7% in accordance with ameta-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: As treatment plays an important role in the management of GDM, it was found that HbA1c levels are not sufficient to detect some obstetric consequences of GDM in the second trimester. It was concluded that evaluations that synchronize HbA1c and OGTT results are necessary for the diagnosis of GDM in the second trimester.