Wow, that's a hard question. As a male (so many would say I don't actually deserve an opinion on this), I'd probably say it is up to the women. This is not the same as other issues, you are at physical risk, you will suffer horrible pain etc. If you swap out that it's a human baby & swap in anything else, say a parasite gets into you & you go to the doctors, say they say it will be fine you just have to wait 9 months, the parasite will them force its way out of you, causing much bleeding, risk of death & the worst pain you've ever experienced, then we get a different answer...but I do realise that this is not your average parasite, but a tiny person, so the issues are WAY more complex (which does show some interesting philosophic issues in itself!). One argument is that you cannot force a person to do with their own body what you want, so if they do not want anything inside them, can you MAKE them do that? Another analogy is say you wake up one day & you are suddenly attached to a sick person, they are in a coma & will die if you disconnect. You didn't choose to be connected to them, so would it be murder if you disconnected yourself (there is no other choices available in this argument, you either stay connected, or disconnect a binary choice). There are obvious differences in this to the actual question, but can you find a perfect one, I don't think so? A lot of people argue that they had sex, so they take the risk, but we have innate sexual desires, it's part of our primate ancestry, we often can't help having sex (I know for me life would be a dull, sad place without it!), I do take precautions, but even so these are not 100%, nothing is, I could become a father any time & yet I haven't planned to, I don't think I'd 'vote' for an abortion if I did get someone pregnant, but I'd accept the final choice wasn't mine in this case as I'm not the person carrying the child & if I was, even if I chose not to have an abortion, that wouldn't mean I could, or should, impose my views onto everyone on the planet.
So, basically my answer is the women decides in the end as they are the one's carrying the child, that may not be perfect by a long way, but until the day when they can build an artificial womb, or transplant unborn babies into new volunteer mothers, then I can't see a better option?