The whole abortion issue is one that, so often, seems to be swayed by emotion rather than reason. Some insist that "abortion is murder" with little to no rationale behind their stance while others talk of "a woman's choice" as if the fact a pregnancy is inconvenient is all the justification required to terminate it. As with many simplistic stances, both seem to struggle to stand up to much scrutiny.
The idea that a woman's choice is sacred struggles in so many ways. Firstly most sexual activity is consensual and therefore the consequences of an act undertaken willingly aren't necessarily something that can be wished away. At some point we have to accept that the consequences of an activity performed entirely voluntarily must be accepted, or else the next logical step is that the presence of a baby in the home is disruptive and inconvenient and it can therefore be terminated. There is also the question of what rights the father should have - if a couple separates during the pregnancy it seems wrong that a father who is willing to raise the child without assistance from the mother should be denied his chance to do so simply because the mother alone has changed her mind and no longer wishes to carry the child she conceived willingly.
Much of the opposition to abortion is also based on little more than emotion - the idea that "life begins at conception" would require that a device such as an IUD or the "morning-after pill" be classified as a murder weapon as it serves no purpose other than to prevent the implantation of a human being into the mother's womb and therefore prematurely end the life of the barely-formed human that ends up flushed away. It also raises questions of whether a zygote that didn't implant in the womb for entirely natural reasons should be considered a death that should be mourned, even though in most cases the mother won't even know what happened.
If the subject is looked at through a scientific and a Scriptural lens we can hopefully shed some light on the relative merits of different stances, although they must be verified through appropriate lenses rather than being seen as the desired end goal and the lenses distorted so as to yield the desired results. The worst thing we can do is merely hunt for a scientific study or a Scriptural verse to support what we want to believe and ignore anything that appears to contradict it. For example, if the only logical conclusion we can draw is that life begins at conception then the potential inconvenience of an IUD effectively being a murder weapon must be accepted, however unpleasant the thought may be to us.
From a scientific perspective Josiah has already made some very good points about the progression of a zygote-embryo-foetus-baby and the concept that the DNA doesn't change from one stage to the next. However, if we base an argument purely on DNA we end up in all sorts of strange places based on how much DNA we have in common with other living things. From a purely scientific perspective we may argue that the zygote already has the DNA that will cause it to develop into a clearly identifiable human but if we want to accept this as a definitive conclusion then logically we must ask the question of how long human rights last after death, given it is probably safe to assume it takes a while after death for DNA to change.
From a spiritual perspective many people quote verses like Ps 139 or Jer 1:5 as proof that an unborn child is alive, but neither passage proves any such thing. The fact that God knew us before we were born doesn't mean we were alive at that point, nor does the fact that God formed us in our mothers' wombs prove we were alive. When we look at Gen 2:7 we see God formed a man from the dust of the ground and then breathed life into him, at which point he became a living being. So until God breathed life into the man it was a man-shaped thing, made by God, but not alive. Therefore it doesn't automatically follow that a man-shaped thing, made by God (inside the mother's womb) is alive simply because it is identifiable as a man and made by God. If anything this verse would suggest that what makes the man a living thing is the breath given to it by God, and therefore that life begins at birth (i.e. when the baby takes its first breath). If this is the case then aborting a pregnancy at any stage before birth would not class as murder because the foetus is not alive in its own right.
On the other hand, Ex 21:22-25 talks of men harming a woman with child such that she gives birth prematurely and describes how that if any harm follows it must be repaid "eye for eye, tooth for tooth, hand for hand" etc. Although the situation described here is men fighting and incidentally harming a woman, as opposed to an active step targeted at the woman, it appears to assign a value to the life of the unborn child equivalent to that of a born human. If harm to the (as then) unborn child is valued "eye for eye, tooth for tooth" then we can only logically conclude that, Scripturally speaking, the life of the unborn has the same value as the life of the born. The only proviso to this is that such punishment can only be meted out if the woman knew she was pregnant, although in the context of abortion this proviso makes no difference because it is absurd to think of a woman seeking an abortion unless she already knew she was pregnant.
Based on this I struggle to see abortion as being Scripturally acceptable. That still raises the question of what to do in cases of rape or whether continuing with the pregnancy would put the mother's life in danger. From a purely Scriptural perspective the rape issue potentially becomes very thorny, not least because as a man it's easy to come across as dismissive of the consequences of an extreme personal violation and presenting a Scriptural case with little more than "deal with it". However, if we compare it to situations which are at least loosely similar perhaps some clarity appears. If we were sitting in our living room one evening to hear a knock at the door and, when we answered the door, we found an abandoned baby left outside our door in the freezing cold, we would arguably be in a comparable situation. We didn't consent in any way to the succession of events that led to the baby being dumped on us and yet I suspect few would argue it was morally acceptable to merely shrug and leave the baby to die in the cold. We might not be expected to keep and raise the child but to allow it to die through our own inaction would be morally offensive to many. Should it be any less morally offensive to take a direct action to end the life of a baby in a different situation that evolved without the full consent of all participants?
Cases where continuing with a pregnancy would put the mother's life in danger start to create all sorts of moral mazes. If the pregnancy would kill the mother there is obviously a significant chance that it would kill the unborn child in the process, and therefore the insistence that the mother must be sacrificed to save the child seems like pointless posturing given the probability that the child would die anyway. Although the idea of ending one life to save another creates all sorts of moral questions, particularly in this age where organ donation is a viable proposition, I think I would have to come down on the side of tolerating abortion in situations where it is required to save the life of the mother.
However, all this said, there's so much more to the concept of being "pro life" than insisting that pregnant women carry their pregnancies to full term. If all we are going to do when coming from the pro-life perspective is to present a series of arguments that don't affect us and that fundamentally boil down to a stance of "well I wouldn't start from here if I were you" then we have nothing. If the best we have to offer is to stand outside an abortion clinic shouting at the frightened young woman who unexpectedly found herself pregnant and doesn't know how she's going to cope with a baby, calling her a baby killer and showing her pictures of a dismembered foetus in a bucket, we're not helping anyone least of all the frightened young woman. This isn't the kind of love that Jesus told us to extend to others, and offers little more than the prayer of "Dear God, I thank you that I am not like this person here". An argument that is little more than "well you should have kept your legs crossed" will do little other than drive the woman into the hands of the clinicians who promise to make her problem go away right here and right now. If we are to offer a clearly viable alternative to the person who might not want an abortion but who sees little option then we must present an actual alternative. That will almost inevitably mean providing support throughout pregnancy, helping the new mother come to terms with being a mother, possibly helping her to raise the baby (or maybe helping her through the process of deciding whether to keep it or offer it for adoption). Either way taking a stance that expects others to follow a course of action that costs them, when that expectation costs us nothing, impresses nobody. It's easy to write off an argument when the person presenting it has no skin in the game, it's far harder to do so when they put their own money where their mouth is.
This latter part is something of a challenge because I must admit I generally feel disinclined to support the woman who has five children by five different fathers and who is pregnant again. But even there, it's easy to sit in an ivory tower (relatively speaking) and pronounce judgment on those below us, and much much harder to meet them where they are and provide tangible help to break cycles of hopelessness and despair.
