Changes in prepregnancy body mass index between pregnancies and risk of gestational and type 2 diabetes

We investigated whether changes in interpregnancy body mass index (BMI) influence the risk of gestational and type 2 diabetes among a cohort of women with two consecutive live, singleton births of 20-44 weeks gestation (n = 232,272). Logistic regression models were used to examine the risk for development of gestational or type 2 diabetes during the second pregnancy. Mothers with normal weight for both pregnancies (normal-normal) served as the referent group. Across all BMI categories, mothers with significant weight gain (i.e., moving from a lower BMI category into a higher category) had an increased risk for the development of diabetes. Mothers who moved from normal prepregnancy weight (BMI = 18.5-24.9 kg/m(2)) in the first pregnancy to obese prepregnancy weight (BMI a parts per thousand yen 30.0 kg/m(2)) in the second pregnancy showed the greatest increment in risk. These mothers exhibited a threefold risk for developing diabetes (OR = 3.21, 95% CI 2.76-3.73). Mothers who maintained their interpregnancy BMI weight category or who moved to a lower BMI category had reduced risk for gestational and type 2 diabetes. The risk associated with mothers who moved to a lower BMI category was approximately half that of the normal-normal BMI category. Interpregnancy weight gain is associated with a dose-response increase in risk of diabetes. Establishing a normal interpregnancy BMI may reduce the risk of diabetes.