Ok, so you're saying that there could be a list of conditions in which abortion is acceptable, but that list would be lengthy and complicated to deal with all possible defects.
However, after a birth has occurred, killing is not acceptable.
To the first point, I think that we have to be very specific about why we would choose to kill a human. It is a important decision, and so its important to examine the situations in which we think its acceptable, and then to ask, why, in those cases, is it acceptable.
And if we again draw a line, and say that killing after birth is never acceptable, then again, I have to ask why?
What change occurs during birth that suddenly makes killing wrong?
And we could break it down further. At what stage during birth does killing become wrong? Is it when the head has passed through the vagina, or the whole body, or not until after the cord has been clamped and cut?
And again, to each question- why?