The only ethical decision to abort is when the mother's life is in danger.
If you will lose 2 lives, you must do whatever it takes to save at least 1.
Beyond that, if the circumstance does not allow you to kill a newborn, a 2 year old, a 5 year old, a teenager, then that circumstance also does not allow you to kill a child before birth.
To the DUmmies, if you can't see the child, then "it's" just a lump. "It" isn't a child until you can actually see "it." To those with brains, we understand that the child after birth is the same child that was conceived. There is no level of development, no location, no amount of dependence that reduces the humanity of that child...no magic line where "it" becomes "he or she." The "he or she" was there at the moment of conception.