It is not allowed to have intercourse when having menstruation. If you have intercourse during menstruation, you may have the following hazards: First, clinically come to menstruation, mainly vaginal bleeding caused by the shedding of the endometrium. During menstruation, the endometrium is in a state of shedding. If you have intercourse, pathogenic bacteria may enter the uterine cavity along the cervix, causing the possibility of endometrial infection, which may lead to repeated lower abdominal pain due to endometrial inflammation, or clinically dysmenorrhea, or blood clots in menstrual blood. Secondly, sexual excitement is caused during sexual intercourse, and the contraction of the uterus due to orgasm can cause the menstrual blood in the uterine cavity to flow back into the pelvis and lead to endometriosis. Clinically, not only does menstrual pain occur, but it may also lead to infertility.