Try not to have intercourse when you are on your period, it may lead to endometriosis, endometritis, pelvic inflammatory disease and so on. 1. Endometriosis: If you have intercourse during your period, it may cause the backflow of menstrual blood, which will cause endometriosis and dysmenorrhea after a long period of time. 2. Endometritis: After intercourse during menstruation, bacteria in the reproductive tract grow and attack the endometrium, causing endometritis, which leads to abdominal pain, fever, menstrual blood ectasia and other symptoms. 3. Pelvic inflammatory disease: If the endometritis caused by coitus is not treated in time, retrograde bacterial infection will cause pelvic inflammatory disease, resulting in abdominal pain, fever and other symptoms. It is recommended not to have intercourse during the period of great aunt to avoid the above lesions.