It is recommended that for pregnant and postpartum women who have not been diagnosed with pre - pregnancy diabetes or gestational diabetes, a 75 - gram oral glucose tolerance test (OGTT) should be conducted at 24 - 28 weeks of pregnancy and at the first visit after 28 weeks. On the day of the OGTT, the woman should go to the hospital on an empty stomach in the morning. First, a fasting blood glucose test will be done. The normal value is less than 5.1 millimoles per liter. Then, dissolve 75 grams of glucose powder in 300 milliliters of warm water and drink it within 5 minutes. The normal blood glucose values 1 hour and 2 hours after taking the glucose are less than 10.0 millimoles per liter and 8.5 millimoles per liter respectively. If the blood glucose value at any point exceeds the normal range, gestational diabetes can be diagnosed. Women with high - risk factors for gestational diabetes, such as advanced maternal age, overweight or obesity, polycystic ovary syndrome, family history and history of adverse pregnancy and childbirth, as well as those with a fetus larger than the gestational age, excessive amniotic fluid during this pregnancy, and recurrent vulvovaginal candidiasis, are all recommended to undergo the gestational OGTT.