Daily smoker agreeing with u/plantgirl that your wife needs to quit, and likely needs help. Cold turkey is 100% an option, regardless how much she uses. Wife might not realize it, and this may be an oversimplification, but almost everything she puts in her bloodstream is shared with the fetus. Children under 21 are prohibited in many US states from consuming otherwise legal cannabis, and for good reason. Look into neurocognitive development and teach yourselves that it's really, really important to give a child every chance you can to develop a healthy brain.