My wife is also pregnant (does not smoke). I do smoke and will be a father in less than a month. I have to say this is really becoming one of the big WHYs I am trying to quit. It's very life-changing and I hope you also find motivation in quitting for the health of your child. Congratulations btw!
Please remember it is only 9 months.
A recent study was made for ALL effects of long term smokers. It revealed that smoking weed during pregnancy can be VERY damaging to a fetus' nerve development. Remember... Nerves include brain and spinal cord.
I really don't know what to say to "help" you. I know we are on the "quitting" boat but if you feel like you cannot stop only for your child's health, I would recommend professional addiction help. I mean that in the most loving way.
Wishing you the best