The risk of indwelling abortion procedure is higher compared to the usual scarred uterus abortion, conventional abortion or abortion of larger months. The main reason is that there are abnormalities in the coagulation function after the embryo stops developing, and first of all, the embryonic tissue is mechanized and tightly attached to the uterine wall, which makes the operation difficult and may not be able to scrape the uterine cavity clean. Although aspiration is performed under the hysteroscope, there will be significant residuals due to more severe adhesions. Secondly, the pro-coagulant substances produced by the self-fusion of the dead pregnancy and placenta may cause severe coagulation dysfunction when promoting maternal blood circulation, resulting in severe bleeding. Therefore, before surgery, routine blood tests, platelets and coagulation function must be checked, as well as D-dimer. Blood preparation should be done before the surgery. Blood preparation does not mean that blood transfusion is necessary, but mainly for the safety of the surgery. Also if the coagulation function is normal, oral estrogenic drugs should be taken to increase the sensitivity of the uterine muscle to the contractin. During the abortion process, the patient is usually given contractin, which is done to promote uterine contraction and reduce bleeding.