I think that often, in the pro-choice vs pro-life debate people ask the wrong question. The question we should ask is not “Is abortion right or wrong?” The answer to this question is of course of great personal relevance and it is a very important question, but like the question of whether there is a God, I believe it is one that must be left to individuals to answer for themselves.
Whether abortion is right or wrong is a hard question and it ultimately involves drawing an indistinct and necessarily arbitrary line between what is considered sacred human life and what is not. The Catholic church, banning contraception, draws the line at one extreme. There are even people who advocate killing babies that have already been born can be justified (see here), who take the other extreme. The point is that the answer to this question depends on your personal ethical, moral, and religious convictions and that there is good, well-reasoned (even if not unassailable) justification for many viewpoints.
So instead of asking a hard question, let us ask an easier one: “Should the government be allowed to decide whether abortion is right or wrong?” If you accept that the government should be secular, that is that it should not support any one religious view over others, then you might agree with me that the answer is no. Both secularists (often pro-choice) and Catholics (notably pro-life) should be able to live in accordance with their views.
Because the question is so hard and because each individual abortion case is different, legislation is going to be a blunt and unwieldy tool. If you forbid abortion entirely, you also forbid abortion where it would save the mother’s life. As soon as you start making exceptions, you create grey areas, uncertainty. You cannot possibly account for the myriad of circumstances which people may face. There will be unintended consequences such as illegal abortion clinics (yes, this is in fact inevitable) where safety standards cannot be enforced. And you deny people the right to make a very important and difficult choice.
Like free market economists, I believe better outcomes can be attained by giving people as much freedom as possible, only intervening when the market or, in this case social norms and structures, clearly fail. This is why making murder illegal is necessary. The consequences of not doing so may be total anarchy, an inability for society to function because no one feels safe. This is not the case with abortion. Nor is it the case with assisted suicide, to which I think the same principles should be applied. The ones best placed to make the decision are the ones closest to it: they are emotionally invested, they have the most information and their futures depend on it.