The impact of combined gestational diabetes on pregnant women is closely related to the degree of diabetes, the timing of the onset of maternal blood glucose elevation, and the level of glycemic control during pregnancy. Maternal mortality has been significantly reduced in combined gestational diabetes, but those with uncontrolled glucose during pregnancy have a higher incidence of maternal complications. The main complications include preeclampsia, preterm delivery, amniotic fluid overload, ketoacidosis and infection. 1. Pre-eclampsia: Pregnancy combined with abnormal glucose metabolism increases the likelihood of pre-eclampsia and is related to the degree of abnormal glucose metabolism in pregnant women. Pregnant women with pre-eclampsia have increased preterm births of medical origin, perinatal morbidity and mortality. The pathogenesis of the disease is still unclear, but it is considered to be related to insulin resistance, hyperinsulinemia and hemodynamic changes, as well as other related factors, such as the general condition of the pregnant woman, blood pressure in early pregnancy, urine protein, glycated hemoglobin and blood glucose concentration in early pregnancy. The preventive measures for the disease are to enhance pregnancy care, early detection and treatment of abnormal glucose metabolism and hypertension. The principle of treatment is to control blood sugar, control blood pressure, prevent the occurrence of ketoacidosis and eclampsia, ensure the health of mother and child, and reduce perinatal mortality. Preterm birth: Preterm birth is one of the common complications of combined glucose metabolism abnormalities in pregnancy, and the incidence is significantly higher than that of non-diabetic patients. Excessive amniotic fluid is often one of the causes of spontaneous preterm birth, but most preterm births are of medical origin, such as complications of pre-eclampsia, fetal distress and other serious complications, often requiring early termination of pregnancy. Preterm birth is a major cause of perinatal morbidity and neonatal mortality in diabetic mothers. The causes are multiple: hyperglycemia induced intrauterine hypoxia, congenital malformations, fetal hypoglycemia and intrauterine infections. Preventive measures include awareness of self-protection in prenatal care, screening for gestational diabetes, early management of vaginal infections, active prevention of complications, balanced nutrition, rest, and active promotion of fetal lung maturation in cases of preterm labor of medical origin. The delivery method of preterm labor is usually vaginal, but if there are some special circumstances, a cesarean section should be performed. A pediatrician should be present at the time of delivery to participate in resuscitation. 3. Excessive amniotic fluid: it is one of the common complications of gestational diabetes mellitus and has a certain impact on the prognosis of pregnant women and perinatal babies. Its pathogenesis is not clear, and it is related to the control of blood sugar during pregnancy. The etiology is due to fetal malformations, hyperglycemia during pregnancy and fetal placental factors. The effects of excessive amniotic fluid on the mother are weak uterine contractions, placental abruption, gestational hypertension and shock, while the effects on the fetus are premature delivery, abnormal fetal position, fetal distress and intrauterine fetal death. The main preventive measures are to strengthen pre-pregnancy counseling, monitor blood sugar, and use insulin to control blood sugar. In case of excessive amniotic fluid with fetal malformation, terminate the pregnancy immediately; in case of normal fetus, observe closely and continue the pregnancy. 4. Diabetic ketoacidosis: It is a metabolic syndrome with the main clinical manifestations of hyperglycemia, hyperglycemia and metabolic acidosis due to complex metabolic changes during pregnancy, coupled with hyperglycemia and relative or absolute insulin deficiency, causing disorders of sugar, fat and protein metabolism, and further development of accelerated lipolysis and rapid increase of ketone bodies in blood, resulting in water and electrolyte disorders and acid-base imbalance. It mainly occurs in patients with type 1 diabetes combined with pregnancy. The impact on pregnant women and fetuses is great, and it is very likely to cause death of mother and child. The main preventive measures are: reasonable blood glucose level, good patient compliance, strengthening self-testing of blood glucose, reasonable application of insulin and timely communication with medical personnel. In conclusion, diabetic ketoacidosis can be prevented by receiving ideal testing and treatment during pregnancy.