I have a low lying placenta also, seen at my 22 week scan. At 26 weeks it was still low but the doctor told me he isn't worried at all. I also saw his partner who said the same thing....that as the uterus grows the placenta moves. I think especially if it is low lying, and not covering, your chances are even less that it won't move. I asked what worse case scenio would be, and was told that if by chance it didn't move, I would need a c-section. Not my first choice, but not the end of the world either in my book. I know a c-section stinks, but a vaginal delivery doesn't quite seem like a walk in the park either lol. Try not to worry too much, chances are everything will be just fine!