Uterine bleeding is caused by the rupture of blood vessels in the chorion or uterine wall. It is mainly caused by direct violence on the abdomen of pregnant rabbits, which causes damage and rupture of uterine wall blood vessels (maternal blood vessels or chorionic blood vessels) of pregnant rabbits. In addition, uterine bleeding can occur after fetal growth is too large, delivery time is too long, uterine tumor and abortion.