Lindie, my baby was measuring roughly the 'right' gestation at my 18-20 wk scan. I had a 32 wk scan also, to check for placenta praevia, and at 32wks, my baby was measuring 36wks. We were absolutely certain about dates, as it was an assisted conception.

Anyway, my baby ended up being born weighing 4.86kg (10lbs 11.5 oz), 2 days before my due date. So looks like my u/s was right about having a big baby.