Maternal overweight and obesity are associated with increased risk of type 1 diabetes in offspring of parents without diabetes regardless of ethnicity

Aims/hypothesis The incidence of type 1 diabetes in children is increasing in Sweden, as is the prevalence of maternal overweight/obesity. Therefore, the aim of this study was to investigate if maternal overweight/obesity increases the risk of type 1 diabetes in offspring of parents with and without diabetes, and of different ethnicities. Methods The study cohort comprised 1,263,358 children, born in Sweden between 1992 and 2004. Children were followed from birth until diagnosis of type 1 diabetes, emigration, death or end of follow-up in 2009, whichever occurred first. First trimester maternal BMI was calculated (kg/m 2 ). Poisson regression was used to calculate incidence rate ratios (IRRs) with 95% CI for type 1 diabetes in the offspring. Results The risk of type 1 diabetes was increased in offspring of parents with any type of diabetes regardless of parental ethnicity. High first trimester maternal BMI was associated with increased risk of type 1 diabetes only in offspring of parents without diabetes (IRR 1.33 [95% CI 1.20, 1.48]). Conclusions/Interpretation Increasing incidence of type 1 diabetes in children with non-diabetic parents may partly be explained by increasing prevalence of maternal overweight/obesity.