I gained 35lbs during my first pregnancy and baby only weighed 6lbs 4.5 oz term+5. My sister gained 60+ lbs and only had a 6lb baby term+12. Cant say for sure yet but my 2nd is looking a little bigger and I've only gained about 1/2 the weight, so I think a lot of it depends on the biology of the baby, some are just naturally bigger or smaller. I know small babies run in my family, so that probably has something to do with it.