Weird stuff

Ok so this is my second baby, and i am trying to find some information on a comlication i had with my first. i dont remember what it is called. what happended was that right after my daughter was born with the doctor puled on the cord to help get the placenta out the cord just came out...it wasent really conected to the placenta at all. turned out that it was somhow conected to the amniotic sac..weird i know....the nurse had never seen that before, but the my doctor had a name for it he had never seen it, but knew what it was...Anyway i was just wondering if anyone has heard of this or had it and knew what the name is, so i can find out more.
i just wonder how commen it is and if it cound happen agian, my daughter was fine though, we dont know how she was geting any nutrents but she turned out perfectly healthy all the same.