Whether it is a normal birth or a cesarean section, the mother will have obvious discharge of malignant dew, and the time of discharge of malignant dew is usually within 42 days after delivery. For women who are not breastfeeding, the time of menstrual recovery is at least about 6 to 8 weeks after delivery. Therefore, to distinguish whether it is menstruation after delivery, the first thing is to judge according to the time of bleeding. If it is menstruation recovery, it is usually vaginal bleeding more than 42 days after delivery, and it will not bleed within 42 days after delivery. The normal menstrual volume is between 20 and 60 ml, and the menstrual period is about 3 to 7 days, while the total amount of postpartum malaria is about 250 ml. The time when the malaria is clean is usually about 20 to 30 days after delivery, and rarely exceeds 42 days after delivery. If a woman’s nightmare remains unclean after delivery and lasts until 42 days after delivery, it is not necessary to consider it as menstruation, but as an abnormality caused by unclean nightmare. It is often necessary to go to the gynecology department to review the ultrasound as soon as possible to see how the contraction of the uterus recovers, and also to see if there is residual stagnation in the uterine cavity, because when there is residual stagnation, it will lead to unclean nightmare for a long time. If a woman is breastfeeding after childbirth, her menstrual flow will resume around 6 to 8 months after childbirth, or even during the whole breastfeeding period.