Embryo implantation includes the processes of embryo localization in the uterine cavity, adhesion, invasion and endometrial metamorphosis, which is the hallmark and limiting process for a successful pregnancy. There are more reasons why the embryo does not implant, such as problems with the endometrium, problems with estrogen-progestin secretion, and problems with the fertilized egg itself. Abnormal thyroid function, blood pressure and blood sugar abnormalities may have an effect. Embryo does not bed in the case of easy to lead to biochemical pregnancy, some people check many aspects, can not find out the specific cause of the disease, there are also individual differences.