Diabetes mellitus during pregnancy includes two types of conditions: one is the pregnancy of a patient who already had diabetes mellitus before the pregnancy, known as combined diabetes mellitus; the other is the first detection or onset of diabetes mellitus after the pregnancy, also known as gestational diabetes mellitus (GDM). More than 80% of pregnant women with diabetes mellitus are GDM. The incidence of gestational diabetes mellitus varies widely, from 1.5 to 14%, because the diagnostic methods and criteria used have not been fully unified. Most patients with gestational diabetes can recover from abnormal glucose metabolism after delivery, but 20%-50% will develop diabetes in the future. Gestational diabetes is harmful to both mother and child and should be taken seriously, mainly in the following areas: 1. It is mostly seen in patients with poor blood sugar control. High blood sugar can make the embryo development abnormal or even death, so diabetic women should be in normal blood sugar control in pregnancy. 2. It is easy to complicate hypertensive disease in pregnancy, which is 3-5 times of normal women. Diabetic patients can lead to extensive vascular lesions, about 12%-40% with proteinuria and hypertension. When diabetes is complicated by nephropathy, the incidence of hypertensive disorders in pregnancy is up to 50% or more. 3. Diabetic patients have decreased resistance and are prone to co-infection, with urinary tract infections being the most common. 4, excessive amniotic fluid, 10 times more than non-diabetic pregnant women. 5, because the incidence of huge fetus is significantly higher, the chance of difficult delivery, birth canal injury, and surgical delivery is increased. Long labor is prone to postpartum hemorrhage. 6. Diabetic ketoacidosis is likely to occur. The impact on the fetus 1, the incidence of huge fetus up to 25-40%. 2.The incidence of fetal growth restriction is 21%. 3. The incidence of preterm birth is 10%-25%. 4. The rate of fetal malformation is 6-8%. Effects on the newborn 1. Increased incidence of neonatal respiratory distress syndrome. 2, neonatal hypoglycemia. 3, hypocalcemia and hypomagnesemia. 4, the incidence of hyperbilirubinemia, erythrocytosis, etc. increased. People with risk factors for diabetes need to be screened for preconception diabetes during the first pregnancy care early pregnancy after the diagnosis of pregnancy. High-risk factors include: 1. obesity (especially severe obesity), BMI ≥ 28. 2. first-degree relatives with type 2 diabetes. 3, history of GDM gestational diabetes, or history of delivery of a child older than gestational age. 4, PCOS polycystic ovary syndrome,. 5, repeated positive urine sugar, etc. The first check for diabetes includes checking FPG fasting glucose,, GHbA1c glycated hemoglobin,, and performing OGTT, and those who meet the diagnostic criteria will be retested on another day for verification. A 75g OGTT is routinely performed directly at 24-28 weeks of gestation to rule out the possibility of gestational diabetes mellitus. The principles of management of gestational diabetes mellitus are to maintain the normal range of blood glucose, reduce maternal and pediatric complications, and reduce perinatal mortality. Glycemic control includes both dietary therapy and insulin medication. The principles of dietary treatment include: 1. small amount of meals, 4-6 meals a day, more vitamins and trace elements, more crude fiber; 2. food calorie intake of 1800 Kcal/day is appropriate, or can be calculated according to pre-pregnancy weight and weight gain during pregnancy, and make appropriate adjustments. Total calorie allocation: 10% for breakfast, 30% for Chinese food, 30% for dinner, and the remaining 30% is allocated to 2-3 additional meals; 3. Food structure: 50%-60% carbohydrate, 15%-20% protein, 25%-30% fat; 4. Food varieties are mainly green leafy vegetables, soy products, lean meat, fish, eggs and milk, and low sugar content fruits <200g/day. 3-5 days after the diagnosis of diabetes is confirmed by dietary guidance, hospitalization is required to perform blood glucose "profile test" to monitor blood glucose. Blood glucose control standards are: fasting 3.3-5.6 mmol/L; 2 hours after meal 4.4-6.7 mmol/L; night 4.4-6.7 mmol; 3.3-5.8 mmol/L before three meals. Gestational diabetes patients may return to normal blood glucose for a certain period after delivery. However, more than half of patients with gestational diabetes will eventually become type II diabetics in the next 20 years, and there is growing evidence that their offspring are at risk for obesity and diabetes.