Diabetes mellitus is easy to develop during pregnancy. Diabetes mellitus diagnosed during pregnancy is gestational diabetes, which is diagnosed by oral glucose tolerance test at 24-28 weeks of gestation. The reasons for being prone to diabetes during pregnancy are as follows: 1. The placenta during pregnancy can secrete insulin-degrading enzymes, which increase insulin degradation, thus weakening the hypoglycemic effect of insulin. 2. The placenta during pregnancy can also secrete a variety of hormones such as placental prolactin, all of which are antagonistic hormones of insulin and can raise blood glucose. 3. Glucocorticoids, estrogens, catecholamines and other hormones are also secreted more during pregnancy, further antagonizing the effect of insulin and easily leading to a further increase in blood glucose. 4. 4. Increased maternal feeding and weight gain during pregnancy also increase the functional burden of pancreatic β-cells and increase insulin resistance. Therefore, under the effect of various insulin antagonistic hormones, abnormal glucose metabolism is likely to occur during pregnancy, and gestational diabetes will occur in serious cases.