Bright red blood on the 42nd day after delivery is usually abnormal, and may be caused by retained placenta, incomplete restoration of the uteroplacental attachment surface, infection and other reasons. 1. Retained placenta and fetal membranes: due to the degeneration and necrosis of the retained placental tissues adhering to the uterine cavity, they fall off, exposing the blood vessels at the base, thus causing bleeding. 2. Inadequate restoration of the placental attachment surface of the uterus: If the restoration of the edge of the placental attachment is incomplete, it can cause thrombus dislodgement and lead to uterine bleeding. 3. Infection: endometritis is more common, infection causes placental attachment incompletion and poor uterine contraction, blood sinus closure, which leads to uterine bleeding. 42 days after delivery and bright red blood may also be due to factors such as poor healing of the uterine incision after cesarean section, resulting in uterine bleeding. Women should pay attention to more rest after delivery, at the same time should relax, avoid tension, anxiety, any discomfort should be timely to the hospital, under the guidance of the doctor, improve the relevant examination, clarify the cause of the disease, symptomatic treatment.