yvonne, u shld aim to gain abt 13kg (general rule of thumb) thro'out the whole pregnancy if you are normal weight to start with.. More if you start off underweight & less if you start off overweight.. i'm already off the halfway mark.. gained abt 8+kg in 21 wks.. gynae advised to eat more fruits, veges & meat & lesser carbo (rice, noodles, etc).. but finding it so hard to control my weight gain.. keep on craving for comfort food, e.g. baked rice, pasta, brownie ice-cream, etc.. sigh..
jingles, i know of bb's weight from my detailed scan report.. if i'm not wrong, it's an estimate calculated based on your bb's head size, arm bone length & thigh bone length.. measurements taken during detailed scan.. prior to that i was only told of the bb's head to bum length during my normal scans..