Heparin is used in a wide range of conditions during pregnancy, for example, in early pregnancy when human chorionic gonadotropin rises slowly, when embryonic development is delayed, when there are repeated spontaneous abortions, in pregnant women with immune disorders, and in mid- to late-pregnancy when placental abruption occurs and thrombosis is suspected. Heparin is an anticoagulant drug and can exert anticoagulant effects both in and out of the body. Many of the above-mentioned pregnancy disorders are associated with the formation of small veins, microscopic venous thrombosis and poor microcirculation, etc. By using heparin appropriately, microcirculation can be improved for the purpose of treating the disorder or controlling the symptoms. The main reason for using heparin anticoagulation in pregnant women is that the drug has fewer side effects, is safer and does not enter the placenta, so it does not have an adverse effect on the development of the embryo.