Iwama N, et al. - In this prospective cohort study, researchers, for the first time, assessed the differences in the results of 75-g oral glucose tolerance tests (OGTTs) in Japan based on gestational age. Based on their gestational age, 2,578 pregnant women have been divided into 3 categories during the 75-g OGTT: <14 weeks’ gestation, 14–23 weeks’ gestation and 24–32 weeks’ gestation. Using multivariable analysis, the connection between gestational age and the results of the 75-g OGTT were assessed. At the time of the 75-g OGTT, early gestational age was related to high fasting plasma glucose levels and low corresponding plasma glucose levels of 1-h and 2-h. Women who had undergone the 75-g OGTT at <14 weeks’ gestation had significantly higher odds of gestational diabetes mellitus (a common complication during pregnancy) diagnosis based on the currently used criteria in Japan vs women with a gestational age of 24–32 weeks. Overall, the investigators concluded that the 75-g OGTT results varied according to gestational age. Using the same 75-g OGTT cut-off values to diagnose gestational diabetes mellitus, regardless of gestational age, may lead to an increase in the prevalence of diagnosis of gestational diabetes mellitus in Japan.