Maternal gestational diabetes mellitus (GDM) and prepregnancy overweight/obesity [body mass index (BMI) 25 kg/m2] might adversely affect offspring cardiometabolic health. Objective: To assess the associations between maternal GDMand prepregnancy overweight/obesity with adult offspring cardiometabolic risk factors. Design: Longitudinal cohort study (ESTER Maternal Pregnancy Disorders Study and the Arvo Ylppo Longitudinal Study). Setting: Province of Uusimaa and Northern Finland. Participants: At a mean age of 24.1 6 1.3 years, we classified offspring as offspring of mothers with GDM regardless of the prepregnancy BMI (OGDM; n 5 193); normoglycemic mothers with prepregnancy overweight/obesity (ONO; n 5 157); and normoglycemic mothers with prepregnancy BMI ,25 kg/m2 (controls; n 5 556).