Bleeding during sexual intercourse for the first time is caused by the rupture of the hymen. The hymen is a very thin mucous membrane that covers the perimeter of the vaginal opening and contains connective tissue, blood vessels and nerve endings. Therefore, when having sex for the first time, damage to the hymen blood vessels may cause bleeding, which is usually small and may occur in very small amounts. However, if the bleeding is prolonged, it is necessary to exclude the possibility of other diseases, the most common of which is damage to the vaginal wall due to excessive violence, and even the formation of a hematoma. Because the vaginal lining is rich in veins, it can bleed easily and even lead to a hematoma.