Brief ReportIncrease in body mass index during pregnancy and risk of gestational diabetes

•We present a case control study describing gestational weight gain (GWG).•Women with and without gestational diabetes (GDM) were examined.•GDM was associated with greater GWG measured by change in BMI units but not kilograms.•BMI is a better measure of proportionate weight gain in pregnancy.•Future guidelines on GWG should include measurement by BMI units.

We recorded gestational weight gain (GWG) and change in body mass index (BMI) at 28 weeks gestation in 343 vs. 339 women with and without gestational diabetes (GDM). GDM was associated with a greater increment in BMI, but not with increased GWG in kilograms.