Rising Prevalence of Gestational Diabetes Mellitus in Ontario: A Population-based Study.

Objectives: Gestational diabetes mellitus (GDM) is a common pregnancy complication. Studies have shown that the prevalence of GDM is rising worldwide. In this study we aimed to describe the prevalence of GDM in Ontario, Canada, between 2015 and 2021.

Methods: Population-based linked health-care administrative databases were used to identify women with GDM via a validated algorithm. Age-standardized GDM prevalence was described for each year between 2015 and 2021. Crude GDM prevalence trends were stratified according to age and income, and trend over time was evaluated using negative binomial regression.

Results: Crude GDM prevalence was 9.5% within this period, with age-standardized prevalence increasing by 35% over the duration of the study (p<0.0001). Prevalence declined in the first year of the COVID-19 pandemic, but it rose again the next year. Prevalence was directly associated with age (p<0.0001) and inversely associated with income (p=0.04), but these disparities did not change over time.

Conclusions: GDM prevalence is rising, but the transient decline in the first year of the pandemic may reflect forgone GDM screening. Disparities in prevalence by age and income are not worsening. GDM is creating a growing burden for the health-care system, particularly for lower income individuals.