Postpartum lochia refers to the need for the contents of the uterine cavity to be expelled over a certain period of time after childbirth. Postpartum lochia generally lasts about six to eight weeks and is divided into three stages: bloody lochia, serous lochia, and white lochia. The first stage, known as bloody lochia, primarily involves the expulsion of accumulated blood in the uterine cavity. Postpartum bleeding lochia generally lasts about one week after childbirth. During this week, the amount of bleeding gradually decreases, and the color changes from bright red to dark red and then to black. Generally, it is believed that postpartum bleeding lochia should not exceed two weeks. If bleeding lochia persists beyond two weeks, an ultrasound should be conducted to determine whether there are any remnants in the uterine cavity, along with a vaginal examination to check for any abnormalities in the cervix and vaginal walls.