Cisforcat
what's your family been like, historically? Do your family (or the father's family) tend to have big babies? Or are you all small babies?
If you all tend to have small babies, I'd probably worry a bit.
Mind you, at my final growth scan for the eldest he was predicted to be 7lb7 by the birth a week later. In actual fact he was much, much smaller (just over 6lb) so they aren't always accurate anyway.