Consequences of being overweight or obese during pregnancy on diabetes in the offspring: a record linkage study in Aberdeen, Scotland Abstract Aims/hypothesis Maternal obesity in pregnancy is associated with cardiovascular disease and mortality rate in the offspring. We aimed to determine whether maternal obesity is also associated with increased incidence of type 2 and type 1 diabetes in the offspring, independently of maternal diabetes as a candidate mechanistic pathway. Methods Birth records of 118,201 children from 1950 to 2011 in the Aberdeen Maternity and Neonatal Databank were linked to Scottish Care Information–Diabetes, the national register for diagnosed diabetes in Scotland, to identify incident and prevalent type 1 and type 2 diabetes up to 1 January 2012. Maternal BMI was calculated from height and weight measured at the first antenatal visit. The effect of maternal obesity on offspring outcomes was tested using time-to-event analysis with Cox proportional hazards regression to compare outcomes in offspring of mothers in underweight, overweight or obese categories of BMI, compared with offspring of women with normal BMI. Results Offspring of obese (BMI ≥30 kg/m2) and overweight (BMI 25–29.9 kg/m2) mothers had an increased hazard of type 2 diabetes compared with mothers with normal BMI, after adjustment for gestation when weight was measured, maternal history of diabetes before pregnancy, maternal history of hypertension, age at delivery, parity, socioeconomic status, and sex of the offspring: HR 3.48 (95% CI 2.33, 5.06) and HR 1.39 (1.06, 1.83), respectively. Conclusions/interpretation Maternal obesity is associated with increased incidence of type 2 diabetes in the offspring. Evidence-based strategies that reduce obesity among women of reproductive age and that might reduce the incidence of diabetes in their offspring are urgently required.