Heparin is used in pregnant women mainly for recurrent miscarriages and thrombophilia. It is generally required from the initial use to the full term of pregnancy, and should be postponed to the postpartum period if necessary. 1. Recurrent miscarriage: i.e. if there are 3 or more consecutive spontaneous miscarriages with the same sexual partner, and after examination, it is considered to be caused by autoimmune disease or coagulation dysfunction, heparin is usually required to be used throughout the pregnancy. 2. Thrombophilia: If there is venous thrombosis or history of thrombosis, pregnant women should use heparin until 6 weeks after delivery. If the thrombosis is induced by surgery, but has been cured, it can be postponed to 28 weeks of pregnancy and used until 6 weeks after delivery. The specific situation varies from person to person. If signs of bleeding, such as vaginal bleeding, are noticed, the use should be adjusted and may be replaced with a smaller dose of aspirin. It is recommended to go to the hospital as soon as possible for examination and to follow the doctor’s instructions for the use of the medication.