Bleeding caused by postpartum breastfeeding generally occurs within 42 days after delivery, during which the mother has lochia secretion. Breastfeeding promotes the secretion of oxytocin, which acts on the uterus and causes it to contract, facilitating the expulsion of lochia and aiding in the recovery of the uterus. Typically, by 42 days postpartum, the uterus has returned to its non-pregnant size and the expulsion of lochia is essentially complete. Subsequent breastfeeding is not directly related to vaginal bleeding. Another situation is due to the increase in prolactin during lactation; menstrual periods may not have fully resumed in women who are breastfeeding, and abnormal uterine bleeding may occur. As long as the amount and duration of bleeding do not exceed normal menstrual flow, no special treatment is needed.