that's very interesting shannonmb, and makes a lot of sense to me...
My mum started smoking when she was pregnant with me (yeah thanks mum!), and I was an overweight/obese adolescent. Though up until my parents split, i was just overweight (I noticed on the scales it said for a woman my height my weight was the midrange, but that was for a woman, not a really tall 10 year old). I didn't really start stacking on the weight till I lived with only my mum. I notice now, that a lot of my eating habits i learnt off her, so my weight is not necessarily to do with her smoking while carrying me.
My theory is, that women who smoke when pregnant (even though for the last couple of decades its been know that's a really silly thing to do), have a lot less self-control, and are more likely to pass that learned behaviour down onto their children, in a 'i want it and i feel like i need it so i will have it, even though I don't *actually* need it' type of way.
but hey, that's just my opinion