Low molecular heparin is generally not routinely used to preserve fetus during pregnancy. If low molecular heparin is used to preserve fetus during pregnancy, it is mainly indicated when the patient has recurrent miscarriages and is also tested for pre-thrombotic state or immune system disorders, and low molecular heparin calcium can be used to preserve fetus. In this case, the main purpose of using calcium low molecular heparin is to prevent the patient’s hypercoagulable state, so that the patient’s embryonic blood supply is richer and the placenta is not affected by the pre-thrombotic state, which may cause the embryo to stop developing or the embryo to develop slowly. In addition, low molecular heparin can improve the blood circulation of the whole body, improve the immune status of the patient, and increase the chance of embryo survival.