placenta previa 14 weeks

On Sunday night I went to the ER with a gush of red blood. They did an ultrasound and the baby was perfect in there with a strong heartbeat. They couldn't explain the bleeding. I went to my OB and they did another u/s yesterday and explained I have placenta previa and that was the cause of the bleeding. They put me on pelvic rest and told me no heavy lifting or strenuous exercise. She said this normally resolves itself by the 20 week anatomy u/s.