Blood after 15 days of cesarean section may be caused by incomplete restoration of the uteroplacental attachment surface, infection of the uterine cavity, and poor healing of the uterine incision. 1. Incomplete adherence of the uteroplacenta: after delivery of the placenta, the adherent surface shrinks rapidly, and thrombus is formed at the adherent site to stop bleeding. If the uteroplacental attachment surface is incomplete, it can lead to the dislodgement of thrombus and the reopening of blood sinuses, which will lead to uterine bleeding and vaginal bleeding on the 15th day of cesarean delivery. 2. Infection of the uterine cavity: If after cesarean delivery, the pregnant woman has endometrial infection, etc., it will also affect the uterine regeneration and uterine contraction, etc., which will lead to bleeding. 3. Poor healing of uterine incision: If the hemostasis is poor during the operation, forming local hematoma or local tissue infection, necrosis, resulting in poor healing of the incision, bleeding can occur again. If the mother has vaginal bleeding again after 15 days of cesarean section, it is recommended to consult a doctor in time, under the guidance of the doctor, improve the relevant examination, clarify the cause of the disease, and symptomatic treatment.