I know of midwives here who won't take on clients who smoke. They simply see too many complications and often medical intervention is required as the baby has troubles at birth. I'm sure there are lots who have managed to come through a pregnancy unscathed but I'm sure if you look at fetal alcohol stats there are some mothers that still drank plenty through their pregnancy and their babies were incredibly lucky not to have been effect - at least not probably until later in life when their limited concentration has had a detrimental effect on their schooling etc.
Addictions are very selfish in their nature. They work on your brain to tell you that you can not do with out. It will help you make up many excuses to defend it such as "I'm stressed, the doctor says cutting down is better than stopping, I'm doing the best I can, It can't hurt that much right?" etc etc. I know this as I am an ex smoker who was fooled by the addiction for many years but I realised that I was a slave to it. Seriously, you ladies are strong and competent people, you are going to have a baby that you will fiercely defend and protect. You will cope with working while pregnant, growing a little miracle inside you, puking and aching and refluxing. Then you will labour and experience intense pain but you will be strong and deliver the most gorgeous little person in your world. You certainly don't need a silly substance like nicotine as you are much stronger and better than that. As a previous poster stated, cutting down is just a way for your addiction to keep a foot in the door. As soon as some stressful situation occurs (and lets face it, life is made up of them) it will come to the fore and demand you pay it more attention. You may even tell yourself that you are stressed so it is better to calm your self with a cigarette than to stress the baby out it. Wrong! It's the nasty addiction finding a way to stay in your life.
You don't need it, you can spend the money on your baby and you can start showing your baby just how strong you are and that you will do anything to protect the wee one.
Aside from that, as a mother, you have the responsibility to be in this world for as long as possible for this baby. I just lost my mum at the age of 56 from cancer. I am so sad that she will never see my children grow up, and because of her illness she never played the nana role. I never had a mum to talk to about raising babies, pregnancy and she will never celebrate birthdays and christmas's etc. I really need my mum. We all do. So does your baby : ) Don't let your addiction take that away from you and your child.