Gestational diabetes mellitus (GDM) refers to abnormalities of glucose tolerance of varying degrees that occur or are first detected during pregnancy, accounting for about 90% of gestational diabetes mellitus. In recent years, by strictly controlling the blood glucose of pregnant women with gestational diabetes and strengthening fetal monitoring, the comorbidities of pregnant women have been significantly reduced and the perinatal mortality rate has decreased significantly. However, the incidence of recent and long-term complications in mothers and children of pregnant women with diabetes mellitus who have not received timely diagnosis and treatment during pregnancy is still high. In those who have diabetes before pregnancy, the duration of diabetes is longer and the degree of the disease is relatively more severe. If the glycemic control before and during pregnancy is unsatisfactory or if close monitoring is not performed during pregnancy, maternal and child complications will increase significantly. GDM pregnant women with elevated blood sugar mainly occurs in the middle and late pregnancy, when the fetal tissues and organs have been differentiated and formed, so the incidence of fetal malformation and spontaneous abortion in GDM pregnant women does not increase. However, the incidence of fetal malformation and spontaneous abortion in pregnant women diagnosed with GDM in early pregnancy, especially those with elevated fasting blood glucose (FBG), i.e. GDMA2, is similar to that of those with pre-pregnancy diabetes combined with pregnancy. Maternal complications 1. Spontaneous abortion: Hyperglycemia before pregnancy and early pregnancy will affect the normal development of the embryo. If it leads to serious malformation of the embryo, the embryo will stop developing and miscarriage will occur. 2. Pre-eclampsia: The incidence of gestational hypertension syndrome (PIH) increases significantly in people with long duration of diabetes, microangiopathy and poor glycemic control during pregnancy. The incidence of PIH is as high as 54% when diabetes is combined with nephropathy. Once a diabetic pregnant woman is combined with PIH, the prognosis of the perinatal infant is poor, so the occurrence of PIH should be actively prevented during pregnancy. 3, ketoacidosis: ketoacidosis in early pregnancy will increase the incidence of fetal malformation; ketoacidosis in middle and late pregnancy will aggravate the degree of fetal hypoxia and lead to fetal death in the uterus in serious cases, and also affect the development of the fetal nervous system. Ketoacidosis is mainly seen in type I diabetes combined with pregnancy and in GDM patients who are not diagnosed and treated in time. Compared with non-pregnant women, a mild increase in blood glucose of 8.33-13.gmmol/L in pregnant women can cause severe ketosis or even induce ketoacidosis. 4, fetal intrauterine development restriction: mainly seen in pregnant women with diabetes mellitus with microangiopathy. Hyperglycemia in early pregnancy has the effect of inhibiting embryonic development. In addition, diabetes combined with microangiopathy, the placental vessels are often accompanied by abnormalities, resulting in reduced intrauterine blood supply to the fetus, affecting fetal development. 5, excessive amniotic fluid: the cause is less clear, may be related to high fetal blood glucose levels, resulting in high osmotic diuresis and increased fetal urination. Fetal malformation is also one of the causes of excessive amniotic fluid. 6, huge fetus: the incidence of 25% a 40%. It is common in people with GDM and pre-pregnancy diabetes without vascular lesions, and the incidence of huge fetuses in obese pregnant women with diabetes is significantly increased. The incidence of giant fetus is positively correlated with the blood sugar level of pregnant women in the middle and late stages of pregnancy, and the chance of obstructed labor of giant fetus through vaginal delivery increases and leads to birth injury. 7, the incidence of genitourinary tract infection is also increased in GDM patients with unsatisfactory glycemic control during pregnancy. 8, GDM pregnant women 5 to 16 years after delivery, about 17% to 63% will develop type 2 diabetes; recurrence rate of GDM in another pregnancy up to 52% to 69%, and most occur before 24 weeks of gestation. Perinatal complications 1, neonatal respiratory distress syndrome (RDS): fetal hyperinsulinemia has the effect of antagonizing the role of glucocorticoids to promote the synthesis and induce the release of lung type II cell surface active substance during pregnancy, so that the fetal lung surface active substance production and secretion is reduced, resulting in delayed fetal lung maturation and increased occurrence of neonatal RDS. In addition to delayed fetal lung maturation, the occurrence of neonatal RDS in pregnant women with diabetes is associated with the following factors: early termination of pregnancy, cesarean delivery, and neonatal asphyxia. The incidence of neonatal RDS has been significantly reduced in recent years by strengthening the management of diabetes mellitus during pregnancy and delaying the timing of termination of pregnancy. a study by Kjos et al. showed that the incidence of neonatal RDS in pregnant women with ideal glycemic control and delivered after 38 weeks of gestation was similar to that of normal pregnant women. 2, neonatal hypoglycemia: due to the presence of fetal hyperinsulinemia, after leaving the maternal hyperglycemic environment, the incidence of neonatal hypoglycemia can be as high as 30% to 50% if the newborn is not supplemented with sugar in time, which mainly occurs within 12 hours after birth. As the blood sugar level of pregnant women during labor is closely related to the occurrence of neonatal hypoglycemia, the blood sugar of pregnant women during labor should be maintained at 4.4-6.7 mmol/L. Those with elevated blood sugar during labor should be promptly injected with small doses of insulin intravenously. 3, neonatal erythropoiesis: chronic fetal hypoxia can induce increased erythropoietin production, stimulating fetal bone marrow hematopoiesis, which in turn causes increased erythropoiesis, leading to neonatal erythropoiesis, the incidence of up to 30%. After birth, a large number of red blood cells are destroyed and bilirubin production is increased, resulting in neonatal hyperbilirubinemia. If accompanied by asphyxia, it will aggravate neonatal hyperbilirubinemia. 4, neonatal hypertrophic cardiomyopathy: 10%-20% of newborns have an enlarged heart, the cause of which is not clear, mainly in huge children born to pregnant women with unsatisfactory glycemic control. Echocardiography shows heart enlargement, 75% septal hypertrophy, and myocardial hypertrophy. Only a small percentage of newborns present with aspiration difficulties, and in severe cases heart failure will occur. Most of the newborn’s heart enlargement can be restored to normal. 5, neonatal hypocalcemia and hypomagnesemia: diabetic pregnant women are often accompanied by hypomagnesemia, which leads to an increase in the incidence of hypomagnesemia in newborns. About 30% 50% of pregnant diabetic newborns with hypocalcemia, mainly occurs 24 to 72 hours after birth, most of them are asymptomatic, may be related to neonatal hypomagnesemia, followed by a decrease in parathyroid hormone production. 6, renal vein embolism: very rare, the cause of its occurrence is not very precise. If the disease occurs and can not be timely diagnosis and treatment, neonatal mortality is very high. 7. Long-term complications in newborns: the chance of obesity in the offspring of diabetic mothers is increased. Studies have shown that huge children are normal weight at 1 year of age, but obesity appears again in childhood; the onset of type 2 diabetes increases in adulthood. Some studies have shown that breastfeeding delays the onset of diabetes in children. Long-term follow-up results show that the effect of GDM on the intellectual development of the offspring is inconsistently reported. In 2002, Sheffield et al. reported a 6.1% incidence of fetal sarcopenia. The common types of malformations include malformations of the cardiovascular system, such as large vessel dislocation, ventricular septal or atrial septal defects, and single ventricle. The malformations of the central nervous system, such as anencephaly, hydrocephalus, meningocele, spina bifida, and anencephaly. Anomalies of the digestive system, such as anal and rectal atresia. Other malformations include renal hypoplasia, polycystic kidney, pulmonary hypoplasia, and skeletal malformations such as caudal degeneration syndrome. The most common malformations are cardiovascular and neurological malformations, which have the most serious impact on the fetus. The fetal malformations are significantly reduced when the blood sugar of diabetic patients is controlled to normal before pregnancy and maintained in the normal range in early pregnancy. 9. Perinatal death: In recent years, with the emphasis on blood glucose control during pregnancy and strengthening maternal and child monitoring during pregnancy, unexplained fetal death in utero in late pregnancy has rarely occurred, and the perinatal mortality rate has significantly decreased. Patients with diabetes mellitus who were not diagnosed or treated during pregnancy are prone to fetal distress in late pregnancy, and in severe cases, fetal death in utero. The incidence of intrauterine fetal death is as high as 50% in pregnant women with combined ketoacidosis.