Bleeding occurs during menstruation as the endometrium undergoes a peeling, which can cause bleeding at this time. If intercourse is performed during menstruation, the tissue of the uterine lining will reach the pelvis through the fallopian tubes, resulting in endometriosis, which can cause adenomyosis and even ovarian chocolate cysts. If the hygiene of both parties is not well taken care of, and the genitals of the male partner enter the vagina during coitus, there may be the occurrence of cross-infection, which will induce the occurrence of endometritis, tubalitis, and even cervicitis because the cervical opening belongs to the open state. It may also cause menstrual dribbling, due to excessive uterine excitement, may also cause menstrual flow to become heavy, or even cause abnormal bleeding, severe cases of abdominal pain, high fever, during the menstrual period prohibit coitus.