Becky,
Don't have any facts to help you I'm afraid - just some "stories". I have a polyp apparently, which did not interfere with my pregnancy, as far as I know and I have not had problems with. But I have a friend that had one that was causing lots of bleeding to the extent where she was bleeding 3 weeks per month and getting anaemic and she had to have it cut out and now is fine.
Anney