DD born when I was 23, pre-pregnancy weight 7 1/2 stone, put on just over 2 stone, back to 7 1/2 after 3 months (I breastfed, which I think helps, and had a healthy diet, but other than that didn't do anything specific).
DS born when I was 30, pre-pregnancy weight still 7 1/2 stone, put on 3st 3lbs (40% increase!!!!), back to 7 1/2 stone after 3 months (again, I breastfed, and again I had a healthy diet, plus I had a 6 year old to run around after, and I was an Avon lady so lots of walking!).
Since then, I've put on a stone and a half - but to be honest I was too skinny at 7 1/2 stone, and at 9 stone (5'8") and 50 years old, I feel happy in my skin. I actually have boobs now!!!