I stuck my neck out on another question like this, so I suppose I should go ahead and compound my earlier error by responding to this one, too.

I really think that the ethics of having children is more complicated than your examples make it. Each example seems to give a reason not to have children--or at least not to have them as long as the reason continues to apply (for example, one would hope the alcoholic would dry up first, and then reconsider having kids). But a single such reason, it seems to me, does not necessarily rise to the point of duty. If considerations of initial conditions worked this straightforwardly, then most people would have a duty not to have children, because most people would find they have one or more failings that could (or even certainly would) have adverse effects on their ability to raise children. Consider: Are wealthy people the only ones who have the right to reproduce? Does poverty leave one with the duty not to reproduce?

I think that human beings have proven to be remarkable resilient in the face of all kinds of challenges--including especially those presented by imperfect (and sometimes very difficult and dysfunctional) parents, as well as those presented by difficult, painful, or "disabling" genetic conditions. (I put that into scare quotes, because I think there is--quite rightly--more than a little reason to be very cautious about saying that any specific such condition is "disabling" in such a way as to leave the person in that condition such that they would have been better off never being born, as your examples seem to consider.)

Instead, I would count each of your reasons as considerations that should be taken seriously as one deliberates about the decision. If the reason can be removed, then it seems that there would be some ethical impetus to remove it for the sake of the future child. But there are real limits even to this--realistically, how good does one have to be in order to take on this responsibility? My own intuition is that better people make better parents; but there are lots of good people in the world whose parents were neither good people nor good parents.