Recently, there has been an increase in the number of young individuals with obesity, as well as an increase in the number of older pregnant women, resulting in a higher incidence not only of gestational diabetes, but also of diabetes during the first trimester. In addition, there has been an increase in the number of pregnant women with higher-than-normal glucose tolerance that do not meet the diagnostic criteria for diabetes at their first prenatal examination. In such cases, it is important to consider whether it is appropriate to wait until gestational age of 24 weeks to diagnose gestational diabetes via the oral glucose tolerance test or whether early diagnosis and management should be pursued. There is a lack of high-quality research on the appropriate timing and methods for early diagnosis of gestational diabetes. The upcoming results of the ongoing the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) study will provide an opportunity to evaluate the appropriate timing for gestational diabetes diagnosis.