It is a normal phenomenon for a girl to have vaginal bleeding during the first intercourse. There is a very thin fibrous membrane on the outermost part of the vaginal opening, called the hymen, which has small holes, so it does not affect the normal menstrual flow. At the same time, there are a few capillaries on the hymen, so during the first intercourse, the penetration of the penis will cause the hymen to rupture, accompanied by vaginal bleeding, but the amount of vaginal bleeding is usually small, and there is no obvious discomfort, so pay attention to hygiene. However, some women have a tough hymen, or the hymen is rich in blood vessels, so the hymen may be seriously torn during the first intercourse, which may endanger some large blood vessels and lead to a significant increase in vaginal bleeding, and may even cause anemia, or even hemorrhagic shock, so you should consult a doctor in time.