Background
Adverse pregnancy outcomes are more common in women with hyperglycaemia. Many women have suboptimal uptake of HbA1c testing postdelivery.

Aims
To compare pregnancy outcomes among multi‐ethnic women with different degrees of hyperglycaemia during pregnancy, and their association with postnatal HbA1c uptake after the introduction of email reminders.

Materials and Methods
A retrospective and prospective single‐centre study was conducted in South Auckland in 2639 women with early gestational diabetes mellitus (GDM) (diagnosed < 20 weeks), late GDM (diagnosed ≥ 20 weeks), overt diabetes in pregnancy, or known type 2 diabetes (T2DM) during pregnancy. Automated email reminders were sent to general practitioners to increase postnatal HbA1c screening. Results HbA1c during pregnancy increased across the late GDM (n = 1425), early GDM (n = 148), overt diabetes (n = 573) and T2DM (n = 493) groups (P < 0.001). Stillbirth was least common in the late GDM group (0, 0.7, 0.5, and 1.9%, respectively, P < 0.001), as were caesarean delivery (32.7, 45.1, 39.4, and 53.5%, respectively, P < 0.001), large for gestational age (LGA) (14.7, 18.2, 22.3, and 30.5%, respectively, P < 0.001), small for gestational age (8.8, 16.7, 11.0, and 11.1%, respectively, P = 0.02), and preeclampsia/eclampsia (7.7, 9.2, 13.0, and 14.8%, respectively, P < 0.001). LGA and preeclampsia/eclampsia were more common among Pacific and Māori women than European women (LGA, 30.1, 22.7, 10.3%, respectively, P < 0.001; preeclampsia/eclampsia, 13.5, 14.0, and 8.1%, respectively, P < 0.001). Postpartum HbA1c screening increased among women with GDM/overt diabetes after the introduction of the reminder emails (39.6% vs 34.0%, P = 0.03). Conclusions Women with late GDM are least likely to experience adverse outcomes. Email reminders to improve postpartum HbA1c screening warrant further investigation.