Glucose tolerance is also known as glucose tolerance screening, if there is no abnormality in the previous pregnancy test, it is recommended to do it around 24 to 28 weeks of pregnancy is more appropriate, if there is diabetes and other conditions before pregnancy, there is no need to do further glucose tolerance test. Glucose tolerance screening can diagnose whether a pregnant woman has gestational diabetes, glucose tolerance test should be fasted for 8 to 12 hours before the test, the first fasting blood test in the morning, then drink 75 grams of glucose water, and then take another blood test at an interval of one hour or two hours, according to the results of the three blood tests to determine whether a woman has gestational diabetes. Gestational diabetes mellitus has a greater impact on the mother and child, and may cause ketoacidosis and hyperglycemic coma in the mother, resulting in fetal developmental abnormalities, excessive amniotic fluid, and macrosomia. It is recommended to follow the doctor’s instructions to carry out various tests.