Maternal prepregnancy BMI and physical activity and type 1 diabetes in the offspring.

Background Previous studies showed conflicting results on the association between maternal pre-pregnancy body mass index (BMI) and type 1 diabetes in the offspring, and the role of maternal pre-pregnancy physical activity is unclear. We aimed to assess whether maternal pre-pregnancy BMI and physical activity predict type 1 diabetes in their offspring. Methods Prospective study including women participating in the Nurses' Health Study II with follow-up from 1989 to 2011. Women repeatedly reported their BMI and physical activity, from which pre-pregnancy exposures were derived; and retrospectively reported their BMI at age 18 and physical activity at ages 18-22, considered early adulthood exposure. We estimated risk ratios (RR) and 95% confidence intervals (95%CI) using generalized estimating equations, adjusted for covariates. Findings at p Results We identified 276 cases of type 1 diabetes among offspring (n=70,168) with maternal pre-pregnancy information and 448 cases among offspring (n=111,692) with maternal early adulthood information. Pre-pregnancy and early adulthood maternal BMI and physical activity were not associated with offspring type 1 diabetes. The RR comparing overweight to normal weight mothers was 1.08 (95%CI: 0.73-1.59) and comparing obese to normal weight was 0.94 (95%CI: 0.49-1.79, p-trend: 0.98). Comparing highest to lowest quartile of maternal physical activity the RR was 0.90 (95%CI: 0.61-1.32; p-trend: 0.73). Maternal type 2 diabetes was associated with an increased risk of type 1 diabetes in the offspring (RR=1.87; 95%CI: 1.25-2.80). Conclusions Our findings do not support a relationship between maternal pre-pregnancy BMI or physical activity and the risk of type 1 diabetes in the offspring. This article is protected by copyright. All rights reserved.