There are more reasons for small amount of bleeding after sex, which may be caused by cervical lesions, trauma, before and after menstruation and so on. 1. Cervical lesions: if there are cervical polyps, cervical erosion, cervical cancer and other diseases, due to the cervical region of the tissues are relatively fragile, when sex collision stimulation of lesions of the tissues, vaginal bleeding may occur. 2. Trauma: It is common to see vulvar lacerations and vaginal tears caused by over-excited behavior during intercourse, thus causing bleeding and pain symptoms. 3. Before and after menstruation: If the woman’s pelvis is congested before and after menstruation, it may cause vaginal bleeding after sex. There may be other reasons for small amount of bleeding after sex, it is recommended to go to the hospital in time for examination, under the guidance of professional doctors to clarify the cause of the disease, targeted treatment, so as to avoid delaying the condition.