Normal sex during menstruation basically will not be pregnant, because at this time the endometrium is in the shedding stage, and in the ovary although there are follicles but will not reach the dominant follicle that will not be ovulated, so there will be no accidental pregnancy. But menstrual intercourse will cause harm to the body, intercourse on the cervical mucosa, vaginal mucosa and endometrium may cause corresponding pathogenic bacteria infection, causing local inflammation. In serious cases, it can also lead to pelvic infection and pelvic inflammation, and even lead to tubal adhesion and infertility, the damage is still relatively large. So do not have intercourse during menstruation, keep the vulva clean, change sanitary napkins.