The Bernese gestational diabetes (GDM) project: Early hemoglobin A1c (HbA1c) as a predictor of GDM

Gestational diabetes mellitus (GDM) is an increasingly condition with proven maternal and fetal morbidity. At present, there is no effective method of prediction in early pregnancy. Therefore our aim was to investigate if HbA1c could be an early predictor in our cohort.

We performed a prospective study with an HbA1c test at ≤14 weeks of gestation. The primary outcome was GDM development. Women with an HbA1c value < 5.7% were compared with those in the prediabetic HbA1c range of 5.7 – 6.4%. Statistical significance was considered when p-value < 0.05.

668 women met inclusion criteria: 636 of them had an HbA1c level of < 5.7% (group 1), and 32 (4.7%, group 2) > 5.7%. The prevalence of GDM in the entire study population was 98/668 (14.6%). Women in the second group had a 5-fold increased risk to develop GDM (HbA1c 5.7 – 6.4%: 77% vs. HbA1c < 5.7%: 15.2%, p = 0.0039). Although the incidence of GDM was near 80% in group 2 the weight gain was significantly lower (p = 0.0058). Additionally, women who later developed GDM had significant higher first trimester HbA1c (GDM: 5.20% vs. no GDM 5.15%; p = 0.01). Women with HbA1c < 4.5% did not develop GDM.

Our data in our unselected population demonstrate that women with an early HbA1c > 5.7% are at higher risk to develop GDM. Therefore it could serve as a tool to reduce oral glucose tolerance tests and prospective studies should focus on early intervention in this group versus standard management concerning maternal as well as neonatal outcome.