Glycated hemoglobin and risk stratification in gestational diabetes: An editorial perspective

Abstract

The diagnosis of gestational diabetes mellitus (GDM) is based on an oral glucose tolerance test (OGTT) performed according to the Carpenter-Coustan or the International Association of Diabetes and Pregnancy Study Groups criteria. Although universally recommended, the OGTT has limitations, including logistical challenges, poor reproducibility, and inability to detect antecedent glycemic exposure. These shortcomings have prompted interest in alternative markers such as glycated hemoglobin (HbA1c), alone or in combination with fasting plasma glucose. The established role of HbA1c, however, remains limited to ruling out pregestational diabetes in the first trimester. Additionally, elevated values in early pregnancy that do not reach diagnostic thresholds for diabetes may help identify women at risk of developing GDM and related complications. Currently, HbA1c is not used to diagnose GDM at 24-28 weeks because it underestimates maternal glycemia due to pregnancy-related hematologic changes. Emerging evidence indicates that elevated HbA1c at this gestational age independently predicts adverse perinatal outcomes beyond GDM status itself. While OGTT remains the standard for diagnosing GDM, this editorial explores the current evidence on the possible role of HbA1c as a complementary tool for risk stratification. HbA1c ≥ 5.9% (41 mmol/mol) appears to identify women at increased risk of adverse outcomes in both early and late pregnancy. However, prospective studies are needed before HbA1c can be integrated into risk-based care pathways.