Bleeding from the vagina either during or just after sexual intercourse is never normal and should always be checked by a doctor.A variety of vaginal, cervical or uterine conditions can lead to bleeding from sex, such as common inflammation, various sexually transmitted diseases or abnormal growths that can include cancer.Here's a rundown of the leading causes of bleeding associated with sex:Inflammation: On the cervix, a benign condition called cervical erosion involves an inflamed area on the neck of the uterus. It's often found in young girls, women taking birth control pills and pregnant women, whose cervices are softer than normal. Cervical erosion may need treatment, which includes freezing affected areas, but it can also disappear spontaneously.Atrophic vaginitis - Some menopausal women bleed after sex because diminishing estrogen levels cause thinning of the vaginal walls, which can become irritated from intercourse. This is called atrophic vaginitis, a condition that can be alleviated by using lubricating gels during sex. It can also be treated with estrogen, either locally delivered to the vagina or taken systemically.Sexually transmitted diseases(STDs) such as chlamydia and gonorrhea are caused by bacteria passed between partners during sexual contact. In women, these common STDs attack cervical cells and can cause not only bleeding, but a variety of other symptoms, such as vaginal discharge and pelvic pain, itching and burning. They are treated with antibiotics. Left untreated, chlamydia and gonorrhea can lead to infertility.Trichomoniasis is another type of vaginal infection. Trichomoniasis is caused by a single-celled parasite that is usually spread through sex. In addition to causing bleeding after sex, it can also cause vaginal discharge and itching.Abnormal growths on the vagina, cervix or uterus can all lead to bleeding during or after sex. While cancerous or precancerous growths are certainly a concern, "abnormal" doesn't necessarily mean "cancerous." A variety of other growths can also lead to bleeding.Endometriosis occurs when endometrial tissue, which normally lines the inside of the uterus, appears outside of it. Endometrial tissue can attach to the surface of organs in the abdomen, causing excruciating pain and potentially leading to infertility. When endometrial lesions appear on the cervix or in the vagina, they can prompt bleeding during or after sex.Uterine polyps are small, soft lumps of endometrial tissue protruding inside the uterus. Intercourse-related bleeding can result from these polyps, which may also appear on the surface of the cervix. Polyps can also prompt bleeding between periods or after menopause. Sometimes polyps disappear by themselves, but treatment can include surgery.