Context
The risk of gestational diabetes mellitus (GDM) differs between the Danish population and several migrant groups. However, it is unclear if the incidence and timing of type 2 diabetes mellitus (T2DM) following GDM vary similarly.

Objective
This work aimed to investigate the incidence of T2DM according to migration background based on country/region of origin among women with a previous GDM diagnosis and to explore the role of time since GDM diagnosis on the association.

Method
Using nationwide registry data, we followed women diagnosed with GDM in Denmark during 2004 to 2018 to December 31, 2020. Poisson regression models were used to estimate incidence rates (IRs) of T2DM according to country/region of origin, adjusted for age, education, and body mass index.

Results
The study included 20 873 women with a GDM diagnosis, of whom 22.3% were of migrant background and 77.7% were Danish. The mean follow-up time was 7.3 years, and 10.9% were registered with T2DM during the study period. Generally, migrant women had higher IRs of T2DM compared to Danish women, with substantial variations in risk between migrant groups. Women from Pakistan and Sri Lanka had 3 to 4 times higher IRs compared to Danish women. The timing of T2DM onset also varied, with women from Sri Lanka and Pakistan having an earlier onset of T2DM compared to other migrant and Danish women.

Conclusion
This study demonstrated that country/region of origin is an important risk factor for T2DM in women with GDM. These findings underscore the importance of prevention programs targeting women with GDM and a high-risk origin.

type 2 diabetes, gestational diabetes, migration, register-based research, epidemiology