My scans with all mine put them at above average for size because of their long limbs (my husband is a giant).

With DD1 though, I had a scan the day before she was born, they put her head circ at around 40cm - and her belly the same size. And said she would be around 10 pound 4.

She was born the next day at 8 pound 11. Oh, and her head was 35cm. So I don't really trust the scans that much LOL