I asked this question myself a few months ago lol. I was diagnosed with one at about 9 weeks i think but i never bled and it went away by18 weeks or so.
I had one with my daughter. I had bleeding at about 9 weeks which stopped and then again at about 12-13 weeks. I was scared but it did go away. Normally they will do ultrasounds to keep an eye on it but take it easy and rest and it should go away with time.