This observational study compared inter-ethnic antenatal screening practices, including the uptake of both the first-antenatal blood screen and the universal two-step gestational diabetes (GDM) screen recommended at 24–28 weeks’ gestation, to establish the potential benefit of universal HbA1c testing in early pregnancy to detect unrecognised type 2 diabetes and prediabetes. The study included 11,580 pregnancies in Christchurch, New Zealand, during 2008–2010. Electronic databases were used to match maternal characteristics to first-antenatal bloods, HbA1c, and GDM screens (glucose challenge tests and oral glucose tolerance tests). Overall uptake of the firstantenatal bloods versus GDM screening was 83.1% and 53.8%, respectively. GDM screening was lowest in Māori (39.3%), resulting in an incidence proportion ratio (IPR) of 0.77 (95% CI, 0.71 to 0.84) compared with Europeans. By including HbA1c with the first-antenatal bloods, the number screened for diabetes increased by 28.5% in Europeans, 40.0% in Māori, 28.1% in Pacific People, and 26.7% in ‘Others’ (majority of Asian descent). The combined prevalence of unrecognised type 2 diabetes and prediabetes by New Zealand criteria, HbA1c ≥5.9% (41 mmol/mol), was 2.1% in Europeans, 4.7% in Māori (adjusted IPR 2.59; 95% CI, 1.71 to 3.93), 9.5% in Pacific People (aIPR 4.76; 95% CI, 3.10 to 7.30), and 6.2% in ‘Others’ (aIPR 2.99; 95% CI, 2.19 to 4.07). When these prevalence data were applied to the 2013 NZ national birthing data, routine antenatal HbA1c testing could have identified type 2 diabetes in 0.44% and prediabetes in 3.96% of women.
