Well done for stopping!
A friend of mine has twins - hard won, IVF twins. She cut right down to one or maybe two little rollups a day but somehow could never completely stop.
The twins were born 8 weeks early and spent 9 weeks in SCBU and NICU. Both are now four and both have asthma. They both get chest infections and bronchitis regularly and have spent two out of four Christmases in hospital.
She hasn't smoked a cigarette since the day they were born.
She was told that it wasn't her fault, that twins often come early, that asthma can be caused by lots of things including preemie birth. She told me once that no matter how many people tell her that, she will never, really know that she didn't do that to her babies, for the sake of a couple of cigs a day. The guilt really gets to her, even now, even years later. She won't let anyone persuade her it wasn't her fault - and he says that will never go away fully. Every single time she has to give one an inhaler, or a nebuliser, or sit in hospital with them.
You are doing absolutely the best thing for your baby by stopping. You are giving him or her the love you will have when they're here now, while they are in your tummy, and every time you don't have a cigarette, you are giving yourself and them a gift, and you are loving him or her a little more. Well done to you - stopping smoking is the first selfless act of love you can do for your new baby :)