The sudden appearance of bleeding in the fifth month of pregnancy is considered to be the occurrence of miscarriage. Bleeding should not occur during pregnancy, and after the appearance of bleeding, an ultrasound should be done to determine the situation. If you have obvious stomach pain, cramping or distension, you should use birth control medication in time to prevent miscarriage. If there is only bleeding and no obvious stomach pain, it is considered to be caused by placenta praevia or placenta marginalis, which can be accurately determined by ultrasound. If it is determined to be caused by placenta praevia, you should pay attention to absolute bed rest in order to avoid increased bleeding.