Let's first dispense with "pro-life". To its credit, the Catholic church has attempted in these past decades to enlarge this stance beyond abortion. They Catholic church stands against capitol punishment, for instance, and against assisted suicide as a part of its pro-life stand. Gotta give them credit for attempting consistancy.
However, official Catholic doctrine still has a just war theory, and just war theory says that, if someone is seriously endangering your nation or threatening the freedom of its inhabitants, war with all its killing is justified. The nation at war must have tried all other routes to solve the problem and must attempt to avoid killing non-combatants, but there is a place in Catholic doctrine where, when fundamental human freedom clashes with life, freedom wins.
Well, I have to say, that I know of no more fundamental clash between freedom and life than that which takes place within and around every unwillingly pregnant woman, who is giving up huge chunks of her freedom for the sake of the life of another...for nine months if she can bear to give away the baby for adoption, and for at least 18 years if she can't. The fact that this is never discussed points to the fact that there's something else going on in our minds and hearts,
And it is.
The REAL doctrine underlying abortion restriction is the (old but still powerful) doctrine that sex is for procreation. Since you should never have sex unless you want to have a baby, then if you do have sex and get pregnant, you should accept the consequences.
The newer version of this doctrine is that every act of sex should be open to the possibility of creating new life, which, in a culture in which we don't need any more babies and in which every baby is a significant burden as well as a joy, amounts in practice to the same thing. Shall we have sex tonight, honey? Well...maybe not.
These are the doctrines that lie behind the church's prohibition of artificial means of birth control, which most Catholics and others don't support. But they are unconsciously powerful.
Look, for instance at the fact that, besides an exception if her life is in danger, the most common exception in anti-abortion legislation is the exception in cases of rape and incest. Why those exceptions? Because in that case, the woman didn't choose to have sex and shouldn't be expected to take the consequences.
Now I myself believe that it sex is a part of human life for far more than creating babies. Evolution made sex such fun because it's necessary to keep families together over the long haul of the lives of children and grandchildren, who benefit immensely from intact families and care from multi-generations of relatives.
If sex has two legitimate purposes, it is likely that those purposes will sometimes conflict and that conflict has to be managed. Unwillingly pregnant women are not bad people who were doing something illicit and have to take the consequences. Unwillingly pregnant women are bearing the consequences of evolution's duel purposes for sexuality and need assistance.
Or, we could all agree that sex is for procreation and we should only be doing it a few times in our lives. That, too, would solve the abortion problem.