Background
Gestational diabetes mellitus (GDM) is a risk factor for subsequent development of type 2 diabetes mellitus (T2DM). We have investigated the extent of this risk among Māori women without known diabetes.

Materials and methods
We recruited 2786 Māori women aged 28–86 years between 2004 and 2006, without diagnosed diabetes from the Waikato and Southern Lakes regions, via media, community and general practitioner channels, and invited them for an oral glucose tolerance test (OGTT).

Results
Fifty (1.8%) women reported previous GDM (pGDM). The prevalence decreased significantly with age (P = 0.009). Women aged <50 years with pGDM had higher body mass index (35.6 ± 6.7 vs 32.4 ± 7.7 kg/m2, P < 0.01), waist circumference (105.3 ± 18.8 vs 96.9 ± 16.6 cm, P < 0.01), fasting blood glucose (5.5 ± 1.0 vs 5.1 ± 0.8 mmol/L, P ≤ 0.01), two‐hour post‐prandial blood glucose (6.6 ± 3.0 vs 5.6 ± 2.1 mmol/L, P < 0.01) and HbA1c (6.0 ± 0.8 vs 5.8 ± 0.6%, P < 0.05) than women without pGDM. PGDM was a significant risk factor for undiagnosed diabetes (odds ratio 4.0; (5% confidence interval 1.67–9.71). Undiagnosed diabetes was significantly more prevalent among women with than without pGDM aged <40 years (20.0% vs 1.5%). Conclusion Self‐reported past GDM was a significant risk factor for undiagnosed diabetes in this Māori population, particularly among women aged <40 years, highlighting the importance of targeting this group for more intensive screening.