The principle of heparin for fetal preservation, as an anticoagulant drug, its main purpose is to prevent endometrial microthrombosis, thus improving the blood supply to the endometrium. It can be used for habitual or recurrent miscarriages, more than two consecutive spontaneous miscarriages, after a definite diagnosis by a physician. It may be used at the discretion of pregnant women who have high D-dimer levels in order to prevent thrombosis. Because of the risk of bleeding due to improper application, it is important to follow strict medical advice and to monitor blood count and clotting time. It is not recommended to use it blindly for fetal preservation therapy in cases of preterm abortion with underlying conditions that have a tendency to bleed or with a small amount of vaginal bleeding. Sexual intercourse is prohibited in the first trimester of pregnancy and heavy physical labor is avoided.