A small amount of bleeding in the vagina after sexual intercourse is an abnormal performance. The reasons for bleeding are as follows: 1. Some women who have not had sufficient rest after placing the IUD in the uterine cavity and have sex are prone to bleeding. 2. A small amount of bleeding occurs after sex 1-3 days before the onset of menstruation, or 1-3 days just after menstruation, and is caused by a small amount of endometrial shedding. 3. Some women who suffer from cervical polyps, Cervical erosion, endometrial polyps and other diseases, a small amount of bleeding can easily occur after sex. The specific cause is not the same among different individuals and requires proper examination to determine.