The day after menstruation and intercourse with blood, mainly caused by sexual stimulation, the stimulation of sex causes bleeding to occur again, it has a direct link with the preceding menstrual bleeding. Menstruation is actually the renewal of the endometrium. After ovulation and entering the luteal phase, the endometrium grows to a certain thickness, and if early pregnancy does not occur, after 14 days progesterone no longer supports the endometrium, the endometrium will rupture and bleed, and blood and the ruptured endometrium are expelled from the body, which is menstrual bleeding. As time goes on, the endometrium gradually repairs, the bleeding gradually decreases, and menstruation decreases and gradually disappears. However, at this time, the endometrial repair is not perfect, and some locations are like wounds in the human body that have not yet fully grown. One day after the end of menstruation, intercourse occurs again within a short period of time, and the stimulation of sexual life can cause those parts of the endometrium to bleed again. Therefore, intercourse one day after the end of menstruation is likely to occur with bleeding and requires attention.