There are increased studies on the safety of metformin use during pregnancy, and in pregnant women with high insulin resistance and high insulin doses, metformin may be continued or added as appropriate, based on informed consent. However, insulin hypoglycemic therapy is generally preferred. Metformin is an oral hypoglycemic agent, which is mainly used for the treatment of type 2 diabetes mellitus in which dietary control and exercise are ineffective. If combined with insulin, it can also prevent hypoglycemia from occurring, and it also has synergistic effects when combined with sulfonylurea hypoglycemic agents. Several studies have shown the benefits of metformin in controlling postprandial blood glucose, reducing weight gain in pregnant women, and the occurrence of severe hypoglycemia in newborns. However, there are no indications for the use of metformin during pregnancy in China, so it needs to be used with informed consent and in strict compliance with medical advice. The use of metformin needs to be under medical supervision, especially during pregnancy.