The causes of gestational diabetes are: 1. pregnancy reasons: in the middle and late stages of pregnancy, the insulin-resistant substances in the body of pregnant women increase, and in order to maintain the normal level of glucose metabolism, the demand for insulin must increase accordingly, resulting in abnormal blood sugar during pregnancy; 2. age reasons: the incidence of gestational diabetes increases because of the increase in the number of elderly pregnant women, and the probability of gestational diabetes is lower in young mothers; 3. diet structure reasons: those who prefer sweets and rice or are obese are more likely to suffer from gestational diabetes.