Gestational diabetes mellitus (GDM) refers to varying degrees of abnormal glucose tolerance that occurs or is first detected during pregnancy, and accounts for 80% to 90% of patients with gestational diabetes mellitus. Pregnant women with gestational diabetes who have poor glycemic control can have many adverse effects on themselves and their offspring, and even form a vicious circle. Therefore, diabetic patients with poor glycemic control before pregnancy and those with abnormal blood glucose during pregnancy must be screened and diagnosed as early as possible. The clear goal of management and treatment of pre-pregnancy diabetes mellitus (DM) during pregnancy is early and strict glycemic control within a satisfactory range; for pregnant women diagnosed with GDM, in principle, the same comprehensive treatment plan based on dietary control, moderate exercise, close monitoring and, if necessary, combined with drug therapy is adopted. Blood sugar control target Traditional oral hypoglycemic drugs are mainly used for T2DM, such as sulfonylureas, all of which can pass the placental barrier and have potential teratogenic effects and may cause persistent hypoglycemia in newborns, etc. They are generally not suitable for use after pregnancy. Although glibenclamide and metformin have not been found to have teratogenic effects so far, no oral hypoglycemic drugs are allowed to be used for GDM in China because of the relatively small amount of relevant research in China. The main drug that is recognized as safe for blood sugar control during pregnancy is insulin. The American College of Obstetrics and Gynecology (ACOG) GDM treatment plan proposed in 1994 recommends that every pregnant woman with GDM should have diet regulation, and if fasting blood sugar is still greater than 5.8 mmol/L after 3-5 days of diet control, or if blood sugar is greater than 6.7 mmol/L two hours after meals, insulin should be considered. Since studies have found that the better the blood glucose control, the smaller the incidence of adverse fetal outcomes, the current indicators of blood glucose are lower than this recommended value, such as the guideline published in China in 2014, which proposes that the attainment value is 5.3mmol/L. Dietary control The most important thing about dietary control is to control the caloric intake, therefore, it is necessary to calculate the caloric intake according to the pre-pregnancy weight and the weight gain during pregnancy. For pregnant women with normal pre-pregnancy weight (BMI 20~26), the daily supply of calories is 30kcal/kg, and for obese pregnant women (BMI≥27) 25kcal/kg/day. In late pregnancy, the calorie supply increases by 3% for each additional gestational week. The composition of the general diet requires 50%~55% carbohydrate, 20%~25% protein (at least 75g per day) and 20%~25% fat (saturated fat <3%). The energy distribution of the three meals, generally breakfast should account for 20% of the energy throughout the day, lunch and dinner 35% each, plus 5% of each additional meal between every two meals. If possible, the diet should be adjusted under the guidance of a specialized nutritionist. The occurrence of one hypoglycemia may undo the benefit of long-term good blood sugar control, so when controlling the daily calorie intake, we should also pay attention to avoid hypoglycemia and adjust the diet according to blood sugar in time. Insulin therapy Some clinical studies have concluded that pregnant women with fasting blood glucose >5.3 mmol/L can start insulin therapy one week or even earlier after diagnosis, and the observation period for dietary control in other patients should generally be more than 2 weeks. The number of pregnant women with abnormal glucose tolerance (IGT) and GDM who eventually require insulin therapy is 34% and 46%, respectively. There are various types of insulins, but not all of them can be used for glycemic control in patients with GDM. Among them, long-acting insulins have no significant peaks and last longer than the traditional medium-acting insulin NPH, which allows patients to have more stable blood glucose. The injection dose of insulin and the adjustment method follow the principle of individualization, generally starting from a small dose, and in the absence of acute complications of diabetes, the starting dose of most patients is 0.3~0.8 U/(kg-d), and there are also conservative doses up to 0.2 U/(kg-d). Insulin dosage distribution is generally before breakfast>before dinner>before Chinese food, and needs to be adjusted according to blood glucose trend, not according to individual blood glucose values, and the range of each dose adjustment is 10%-20%, and the closer to the blood glucose attainment value, the smaller the adjustment range. The adjustment of insulin dose should not be too frequent, and generally priority should be given to the adjustment of the corresponding pre-meal insulin dosage with the highest postprandial glucose, and the efficacy should be judged by observation for 2~3 days after each adjustment. The degree of insulin resistance varies in different periods after pregnancy, so it is necessary to adjust the insulin dosage appropriately according to the change of physiological condition. In early pregnancy, the need and consumption of blood glucose are high and patients are prone to hypoglycemia, so the dosage should be reduced appropriately; in late pregnancy, the secretion of insulin resistance hormone increases and reaches a peak around 32 weeks, insulin resistance is obvious, the dose of insulin required increases, blood glucose is unstable and attention should be paid to real-time blood glucose monitoring; during labor and delivery, physical exertion is high, hypoglycemia is prone to occur, pregnant women are emotionally unstable and blood glucose is prone to rise. It is not easy to control the insulin dosage, so it is necessary to closely monitor the patient’s blood glucose and increase or decrease the insulin dosage in a timely manner; during the puerperium, insulin needs are reduced due to the weakening or disappearance of insulin resistance. Regardless of the period, blood glucose monitoring is the main basis for diet control and insulin dosage, and its importance is self-evident. Therefore, regular testing is needed, especially before blood glucose stabilization, one to two blood glucose tests per week is not enough to explain the control of GDM, and it is best to test blood glucose several times a day.