We examined whether pregnant women with a normal glucose tolerance test (OGTT) by New Zealand (NZ) criteria, but elevated HbA1c are a clinically important group with gestational diabetes (GDM). Eighty women with a normal OGTT and HbA1c > 40 mmol/mol, compared with others with GDM, had a significantly higher BMI and were more likely Pacific. Pharmacotherapy was prescribed in 77.5%. Post-partum OGTT and HbA1c were abnormal in 9/43(20.9%) and 27/42(64.3%), respectively. In 1090 women being screened for GDM by OGTT, most women with GDM had an HbA1c ≤ 40 mmol/mol. In the 22.1% of women with an HbA1c > 40 mmol/mol, the OGTT was normal in 61.8%. For centres using HbA1c to screen for underlying prediabetes/diabetes, these data show that a result >40 mmol/mol identifies women who are likely to require pharmacotherapy. An OGTT is still recommended to diagnose GDM, but these data raise questions about a possible role for HbA1c in high risk women with a nondiagnostic OGTT.
Keywords: HbA1c; gestational diabetes; glucose tolerance test; obesity.
© 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.