Ok, and what is your rationale for drawing the line at viability? So if a baby can survive on it's own, it is entitled to trump the "my body my choice," theory of abortion regulation, but if it's a week before that, it has no such rights?
How would you address the discrepancy that some babies are more viable than others at, say, 24 weeks? How would you address the ever-improving field of post-natal care that by the year gets better at keeping premature babies alive? Is this a sliding scale and the legislation gets changed every time there is a development?
You catch my drift?
Maybe that answers your question of "but why 6 weeks?"
How about when someone develops a perfect artificial womb and any embryo can be viably transplanted and brought to term?