Screening for gestational diabetes is usually performed at 24-28 weeks. For diabetes screening, you should fast after 9:00 pm the day before and drink plain water. Blood will be drawn on an empty stomach, followed by glucose water, then one hour later and another two hours later. The normal values of the three results are 5.1mmol/L for fasting blood sugar, 10.0mmol/L for 1 hour after taking sugar, and 8.5mmol/L for 2 hours after taking sugar, and any of these values exceeds the standard, it can be diagnosed as gestational diabetes.