Hi hun,
It is so hard, I know where you're coming from. With my second I too smoked throughout my pregnancy and gave birth at 38wks to my DS who wighed 7lb4oz. My DD weighed 5lb9oz and by then I had quit smoking. My other DD was 6lb13oz and I didn't smoke with her either.
I know the guilt you are feeling but remember you tried your best and at least you have cut down.

Regards,
Dianne