Janey,
I also dunno. I think they are just hazarding a guess. I mean, sometimes after eating a full meal, the tummy sure looks rounder mah, as compared to, say, in the morning. So very subjective.
Btw, how did u put on 4-5kg? M in my 13th week, but think I've barely put on 1kg. I've heard of pple putting on as much as 20+kg during their pregnancy, but was wondering how it could be done. Do I have to force myself to eat? I'm already eating very normally, eating as and when I'm hungry. So how much more ravenous will I have to be?