maybe it's just a 2nd opinion on the fact whether yours is a completly healthy pregnancy?
All I know is with my first baby, the 34 week scan said he was gonna be a whopper, even though I had a pretty small bump.
"You don't look that big because you're fit", said consultant 1.
"You don't look that big because you're tall", said consultant 2.
"The baby really doens't feel that big", said community MW, prodding me 2 weeks later.
No awards for guessing who was right, I would trust the MW to be most informed, too.