Pregnant women who are too fat are more likely to cause gestational diabetes. Due to hormonal changes in the body, the sensitivity to insulin decreases and insulin demand increases with the increase of gestational weeks. Pregnant women with limited insulin secretion are prone to gestational diabetes. Obese pregnant women with enlarged fat cells and increased free fatty acids are prone to insulin antagonism, causing gestational diabetes. Not all obese pregnant women are suffering from gestational diabetes, obese women before pregnancy reasonable weight control, after pregnancy to eat a reasonable diet, to limit due to strengthen the nutrients lead to nutritional excess. Appropriate exercise, regular checkups, reasonable control of blood glucose levels, reduce the adverse effects of gestational diabetes on pregnant women and fetuses. Pregnant women with gestational diabetes mellitus need to control their blood glucose reasonably during pregnancy under the guidance of a professional doctor, and appropriate medication should be given when necessary.