I don't know about the gender thing, but since being pregnant, DD (16 months old) has been obsessed with touching my tummy. She is always lifting my shirt up and pointing to it and even leans forward to touch it when she is sitting in the supermarket trolley!
She gets picture books off the book case for me to read and has recently started to choose 'There's a house inside my mummy' EVERY time - previously she was never interested in that one.
Could just be coincidence - she's probably just surprised that Mummy seems to be getting fat all of a sudden LOL!! But who knows?

Good luck at your scan today.