What is the basis for the Catholic teaching that abortion is immoral/sinful? What is the doctrinal basis for the Catholic teaching that abortion is immoral?  I understand that these will be based on Scripture, but will likely come from official Catholic documents.

So, I'm specifically looking for an answer from a Catholic doctrinal position rather than a purely exegetical answer (as provided to my previous question).
The Catholic catechism has a section on abortion (2270-2275).  It starts with this:

Human life must be respected and protected absolutely from the moment of conception. From the first moment of his existence, a human being must be recognized as having the rights of a person - among which is the inviolable right of every innocent being to life.
Before I formed you in the womb I knew you, and before    
you were born I consecrated you.

 
 My frame was not hidden from you, when I was being made in secret, 
 intricately wrought in the depths of the earth.7

ccc 2270

Essentially, the position is that at the moment of conception, the embryo is fully human, that it should be &quot;treated from conception as a person&quot; (CCC 2274).  Because of that, destroying the embryo (or worse, the fetus) is murder.  Therefore, the ban against abortion is based on the fifth commandment (do not murder).