My Obstetrician never even bothered weighing women during pregnancy, he said it was far too inaccurate as it could be fluid, weight - anything. And he is a well known fertility/ivf specialist Ob Gyn so he can't be making it up.

I put on almost 30kgs with each pregnancy, I think more like 25kgs but I am the smallest I have been that I can remember - i think I started out at 72kgs and now after two babies I am 65kgs and still going down.