To all anti-abortion people here: imagine you had a thirteen year old daughter and she got pregnant, what would you do?
I would explain to her that with the use of sexuality comes responsibility, and since she is not ready to handle it herself (see: having sex and getting pregnant in the first place), the decision whether or not to keep the child is not hers, but that of her parents (who also, hypothetically
of course, will be locking her up in the basement until she can't remember what a boy looks like!). Her child will be born, by the grace of God, and we will go from there as far as figuring out what to do with the baby. (Raise it, adoption, etc.; It's hard to know what to hypothetically do with a hypothetical baby, a hypothetical oversexed and confused child, and a hypothetical wife, plus all the other hypothetical family who conceivably have their own advice and help to give.)
And what would you do if she got pregnant from being raped/molested? Would you really deny her an abortion?
Just as it was not her fault that these terrible things happened to her, we do not want to compound the tragedy with even more tragedy by killing a baby. The answer is ultimately the same as for the first question, despite the radically different circumstances.
As Akimori has written, there is no other opinion that is acceptable in Christianity. All this stuff about "burdening her for 9 months" is bunk. You know what's a real burden for the rest of your life? Knowing that there would be a child out there, born of your flesh, a perfect and holy blessing of God (even if conceived in very unholy circumstances), who is not walking upon this earth as s/he should be so that you wouldn't be "burdened" for 9 months of your life. 9 months is a relatively short measurement of time, not a life in toto. A baby is a life. The two are not comparable.