Just don't listen - everyone is an expert.

This is my history -

OMG - you are TEENY! 8 pound baby girl.
OMG - you are MASSIVE - 6.5pound boy.
OMG - you are HUGE, look at your BOOBS - 6 pound girl.

No one gets it right. If they say you are huge - agree. It ususally shuts them up.