Gestational diabetes includes two parts, one is the presence of diabetes before pregnancy, and the other is the discovery of diabetes after pregnancy, the diagnosis of these two parts is actually not the same criteria. If the patient has been diagnosed with diabetes before pregnancy, this is part of the patient, and after pregnancy, the patient will definitely have gestational diabetes; if there are high risk factors before pregnancy, including obesity, history of gestational diabetes or family history of gestational diabetes in first-degree relatives, or having a huge fetus or excessive amniotic fluid. The diagnosis of combined diabetes mellitus and pregnancy can be made if one of the following four factors is met: 1) fasting blood glucose value ≥ 7.0 mmol/L; 2) 2-hour blood glucose value ≥ 11.1 mmol/L at the time of 75g glucose tolerance test; 3) typical symptoms of diabetes mellitus; 4) random blood glucose, i.e., blood glucose ≥ 11.1 mmol/L at any time point, or Glycosylated hemoglobin ≥ 6.5%. If one of the four items is met and there are high-risk factors, this patient is also diabetic combined with pregnancy that belongs to the first type of gestational diabetes; second, gestational diabetes, the diagnosis is generally done in the 24-28 weeks of pregnancy 75g glucose tolerance test, if fasting blood glucose ≥ 5.1mmol/L, 1-hour blood glucose ≥ 10.0mmol/L, 2-hour blood glucose ≥ 8.5mmol/ L, if the blood glucose value at any of these three time points is higher than the normal standard, then gestational diabetes is diagnosed. Patients with high-risk factors for gestational diabetes or in areas where medical resources are lacking can be diagnosed with gestational diabetes by simply checking fasting blood glucose and having a blood glucose value of ≥5.1 mmol/L.