Mother's decision primarily, as in she hsa the final say, though the father and other family members should have some input. Also to the whole murder therefore never do it and put unwanted kids up for adoption, that is so very naive. It must be nice to be so black and white about something. Truth is, the adoption and foster parents system is completely fucked in many cases and causes a great deal of psychological trauma. Not to mention the huge number of families living in poverty this creates causing yet more suffering for the children and the parents. And don't even get me started on how fucked the human race is if we don't control our population somehow.
Also, the reason this is such a big issue is that the religious whackjobs (mostly in the states) swho eem to think that telling teenagers that condoms and other contraceptive measures don't actually work is a good idea is a HUGE part of the problem because most teens will have sex regardless of whether they are told to abstain or whatever nonsense they are peddling these days. Also, there is a high correlation between teen pregnancy, poverty, and religiosity. There are many people who end up with huge families living in squalor because you know you just gotta be fruitful and multiply cause God says so.
The 99 % thing on condoms is because 1 out of a hundred might fail. NOT that one of every 100 WILL fail. Essentially its just the company covering their asses despite the fact that the actual rate of failure is lower than advertised. Also, birth control pills are a wonderful invention. When used in conjunction with condoms you get to the 99.9% range of effectiveness (again probably lower than actual rate) so in short, birth control works so use it if you want to have sex. Or if you are really, really paranoid, just don't have sex.
Regarding rape, I would never EVER ask a woman to carry a child that was a result of such a brutal act for 9 months against her will. You say adoption but I say you have absolutely no clue as to the psychological trauma that would result from such circumstances. I guess what I'm trying to say is, its all well and good to sit on your high horse and say "its murder so don't do it." But I can't believe you are actually convinced it is that simple. If you are then I don't see the point of discussing it. I've just heard way too many sad stories result from people not having the option or being coerced into keeping a child they don't want by family and religious figures.