I think the most important point to be made here is that no matter what you decide to do for yourself, and how you decide to treat your own body and your life, you have no right to make those decisions with the life of a baby. If there's evidence that smoking weed when you're pregnant can seriously damage your child's growth (and there is), there shouldn't even be a question whether to stop, at least during the pregnancy. If weed isn't addicting, then you can just stop for those nine months. Same with drinking, and cigarettes. You don't want to f*ck up your child's chances because you want to give this child a chance. So stop for the kid.
When the kid's born, don't smoke around it. Second-hand smoke, not matter its source is terrible for you, and especially for your kid. More importantly, exposing your kid to their drunk or high father isn't very good for their well-being. Ask someone who'd know. Seeing your dad drunk is traumatizing when you're 7.
Finally, when you do go back to smoking pot, be responsible. Take care of your family, your kid. Don't let it control you, or cost them. Think this through. Now that you're going to be a father, you have some serious responsibilities.
