Glucose tolerance tests, also known as diabetes screening, have different screening times depending on the population of pregnant women. First, all pregnant women should have their fasting blood glucose checked during early pregnancy prenatal visits to rule out pre-pregnancy diabetes. Second, if a pregnant woman does not have pre-pregnancy diabetes but has risk factors for gestational diabetes, such as an overweight body mass index, obesity, a family history of diabetes, polycystic ovaries, a history of gestational diabetes, and a history of delivery of a macrosomic baby, she will need to undergo a diabetes screening test in mid-pregnancy, which is an oral glucose tolerance test, to rule out gestational diabetes. If a pregnant woman does not have pre-pregnancy diabetes and does not have risk factors, an oral glucose tolerance test should be performed at 24-28 weeks of pregnancy. In high-risk groups, even if the oral glucose tolerance test is normal in mid-pregnancy, another oral glucose tolerance test should be performed at 30 weeks of pregnancy to rule out gestational diabetes. Glucose tolerance test should be performed according to the doctor’s instructions. Once diagnosed with gestational diabetes, blood glucose and body weight should be strictly controlled under the guidance of the doctor to prevent complications.