If you have bleeding, that can be a sign of placenta previa. Many times the placenta will move up as your pregnancy progresses. You may need to be on bed rest and pelvic rest if you have one. If it doesn't move up, they will need to do a C-section to deliver the baby. This will probably be done at about 36 weeks to enable the baby to stay in the uterus as long as possible without. This is also early enough that the mother shouldn't go into labor.
Placenta previa has to be diagnosed by a doctor through the use of sonogram. One sign is bleeding though some women don't have any signs and don't know about it until a sonogram shows a placenta in the lower uterus, sometimes fully or partially covering the cervix.
The risks of placenta previa include not being able to have a vaginal birth and having the placenta tear off too soon which deprives baby of oxygen and nutrients and can cause stillbirth.
If you suspect you have this you must contact your doctor. They will monitor you.