The total flow of black blood after the IUD is considered to be related to endometrial trauma, rejection reaction, intolerance to the IUD and other factors. 1. Endometrial trauma: incorrect operation of uterine placement of the IUD will cause some trauma to the endometrium, so there will be a small amount of bleeding, due to the small amount of bleeding, the blood oxidized in the process of outflow, so the performance of black blood. 2. Rejection reaction: after placing the IUD, there will be some rejection reaction, at this time, the endometrium will appear aseptic inflammation, there will be a small amount of bleeding, but the amount of bleeding is generally less than the amount of menstruation, bleeding time is generally less than a week. 3. Intolerance to birth control ring: If you are allergic, the birth control ring may cause some allergic reactions, and severe allergic reactions may cause prolonged bleeding and even abdominal pain. There may also be other reasons for the black blood after the IUD, so we suggest that you go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.