Twenty days after cesarean section, there is still dark red blood, which is usually abnormal, and may be caused by incomplete repair of the attachment surface of the uteroplacental placenta, poor healing of the uterine incision after cesarean section, infection and other reasons. 1. Inadequate repair of the attachment surface of the uteroplacental placenta: Inadequate repair of the attachment surface of the placenta can cause blood clots at the attachment site to fall off, and the blood sinuses to reopen, leading to uterine bleeding. Thus, there is a cesarean section twenty days and dark red blood appeared, usually the patient’s uterus is large and soft, the mouth of the uterus is flaccid. 2. poor healing of the uterine incision after cesarean section: if the cesarean section operation is poor hemostasis, it will lead to local hematoma or local infected tissue necrosis, resulting in poor healing of the incision. If the downstream branches of uterine artery are cut off at both ends of the transverse incision of the lower uterine segment, resulting in insufficient local blood supply, which leads to poor healing of the uterine incision, it may lead to the emergence of the above situation. 3. Infection: endometritis is more common, which causes poor repair of the placental attachment surface and poor uterine contraction, and incomplete closure of the blood sinuses leading to uterine bleeding. If the mother has a cesarean section twenty days of dark red blood, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor, improve the relevant examination, to clarify the cause of the disease, symptomatic treatment.