Vaginal bleeding during sexual intercourse is commonly caused by the following reasons: 1. damage to the mucous membrane of the skin during sexual intercourse, resulting in bleeding. 2. inflammation of the vaginal mucosa itself, causing capillary rupture after sexual intercourse, resulting in bleeding. 3. polyps in the vagina itself, resulting in contact bleeding after intercourse. 4. chronic inflammation of the cervix, also resulting in contact bleeding. 5. 5. Cervical epithelial lesions and early stages of cervical cancer may cause bleeding after intercourse, so it is recommended to have a gynecological examination for bleeding after intercourse, as well as routine white belt and cervical cancer screening.