Clinically, heparin is commonly used in patients with coagulation disorders, heparin is an anticoagulant drug can prevent the formation of thrombus, when women with pre-thrombotic state, after pregnancy, prone to abnormal placental development, thromboembolism and lead to fetal ischemia and hypoxia, death and other abnormalities, can use heparin to preserve the fetus. The use of low molecular heparin in the absence of thrombosis is to prevent thrombosis. A prophylactic dose can be used, each time using 5,000 units subcutaneously, once a day on a trial basis, throughout pregnancy. Heparin can prevent the formation of thrombosis in the process of use and will not cause the patient to have a tendency to bleed, and it is very safe in the process of use, and only needs to be stopped one week before delivery. If the patient already has a thrombosis, a therapeutic dose of 5000-10000 units intravenously twice a day is needed for the first time.