Low-molecular heparin sodium, as a type of anticoagulant, has a rather important role in fetal preservation. Low-molecular heparin sodium is relatively safe, has relatively low bleeding, and plays a regulatory role in pregnant women who have already experienced fetal instability. The anticoagulant properties of low molecular heparin sodium improve the blood circulation of pregnant women and have a special effect on relieving uterine as well as umbilical vein spasm. The immunomodulatory properties of low molecular heparin sodium can help to suppress some cellular functions and regulate the body’s immunity, with significant therapeutic effects in promoting the fertilization of the egg and the prevention of preeclampsia. Low-molecular heparin sodium has fewer allergic reactions and is safer for pregnant women. For unexplained embryonic abortion and spontaneous miscarriage, low molecular heparin sodium injection in early pregnancy can avoid adverse pregnancy outcome, so low molecular heparin sodium is very important in the treatment of fetal preservation.