Undiagnosed type 2 diabetes during pregnancy is associated with increased perinatal mortality: a large population‐based cohort study in Ontario, Canada

Abstract

Aim To compare perinatal outcomes in women with undiagnosed diabetes with gestational diabetes alone, pre‐existing diabetes and women without diabetes, and to identify risk factors which distinguish them from women with gestational diabetes alone. Methods This population‐based cohort study included administrative data on all women who gave birth in Ontario, Canada, during 2002–2015. Maternal/neonatal outcomes were compared across groups using logistic regression, adjusting for confounders. A nested case control study compared women with undiagnosed type 2 diabetes with women with gestational diabetes alone to determine risk factors that would help identify these women. Results Among 995 990 women, 68 163 had gestational diabetes (6.8%) and, of those women with gestational diabetes,1772 had undiagnosed type 2 diabetes (2.6%). Those with undiagnosed type 2 diabetes were more likely to be older, from a lower income area, have parity > 3 and BMI ≥ 30 kg/m² compared with gestational diabetes alone. Infants had a higher risk of perinatal mortality (OR 2.3 [1.6–3.4]), preterm birth (OR 2.6 [2.3–2.9]), congenital anomalies (OR 2.1 [1.7–2.5]), neonatal intensive care unit admission (OR 3.1 [2.8–3.5]) and neonatal hypoglycaemia (OR 406.0 [357–461]), which were similar to women with pre‐existing diabetes. The strongest predictive risk factors included early gestational diabetes diagnosis, previous gestational diabetes and chronic hypertension. Conclusions Women diagnosed with gestational diabetes who develop diabetes within 1 year postpartum are at higher risk of adverse pregnancy outcomes, including perinatal mortality. This highlights the need for earlier diagnosis, preferably pre‐pregnancy, and more aggressive treatment and surveillance of suspected type 2 diabetes during pregnancy.