Gestational diabetes is a concept that can be easily misunderstood among patients, and what is gestational diabetes needs to be said in both a broad and narrow sense. Gestational diabetes is a broad concept, and there are two types of gestational diabetes: one is diabetes that was originally present, but then the pregnancy occurred, and this is medically known as combined diabetes. The other type of diabetes is a condition that is normal but first appears during pregnancy, and its onset is related to the specific physical state of pregnancy. The former type is just a continuation of the previous condition, and its cause is the same as that of ordinary diabetes mellitus, only aggravated during pregnancy. The latter type is due to the special physical condition during pregnancy, i.e., eating more, exercising less, and the increase in secretion of various insulin-resistant hormones during pregnancy, resulting in a relative lack of insulin secretion. The latter type of diabetes is caused by the special state of the body during pregnancy, i.e., eating more, exercising less, and increasing the secretion of various insulin-resistant hormones during pregnancy, resulting in relatively insufficient insulin secretion. The characteristics of the body state during pregnancy are: (1) The blood volume increases during pregnancy and the blood is diluted, so the insulin secretion is certain, so the insulin secretion is relatively insufficient after the blood is diluted, which leads to the symptoms of diabetes. (2) Hormones secreted by the placenta have anti-insulin effects in the surrounding tissues, such as placental lactogen, estrogen and progesterone, which also cause a relative shortage of insulin, and this can also lead to the symptoms of diabetes. Therefore, the medical concept of gestational diabetes is caused by the special physical state of pregnancy, and the symptoms of hyperglycemia occur for the first time during pregnancy, which is not the same as diabetes combined with pregnancy.