Before I get into my position in the debate, as a biologist, I want to clarify something:
DNA does not decide gender. The expression of DNA decides gender. People with Y-chromosomes can be born as anatomical females. One specific gene, called SRY, on the Y-chromosome, must be activated in order for an embryo to anatomically become male. If it is in some way suppressed (either naturally through a genetic quirk or artificially through science), then the embryo will remain female. The anatomical structures that the genderless embryo develops can become sex organs of either sex. The male organ (EDIT: its name is censored, apparently) and clitoris both start from the same structure, as do testes and ovaries (fun fact: one of the reasons that it hurts so much to be kicked in the nads is because your body still thinks the testes are inside, and thus the pain reaction propagates through your abdomen too).
And none of this takes into account people who are genetically and/or anatomically of one gender, but psychologically of the other (I believe the appropriate term is Transgendered, though I admit to not knowing much about the phenomenon, beyond it being a real thing).
Now, on to the topic at hand:
I am pro-choice. A woman should have every right to end a pregnancy if she feels it is the right choice. She should never be forced to have one or to not have one. Choice is key.
Ergo, as a man, I almost feel that being anything other than Pro-Choice is wrong. It is not my place to decide what a woman should do with her body.
The various arguments for and against abortion itself are all fair, I feel (rape, economics, maternal health, infant health, religion, politics, etc.) But they all come down to one thing: if the woman feels that abortion is the best possible option, she should have the right to do so.
The fact that she has that right does not in any way impede any other mother, faced with the exact same situation, to make the decision to keep the baby instead. That's the beauty of Choice.
I am married, and my wife and I would like to start having children in the next couple of years. Indeed, we're in the "not trying, but would be happy if it happened accidentally" stage. But if she got pregnant years ago, while we were still dating, and neither of us could support a child, I would not have begrudged her the choice. She could choose to keep it, and I'd be there. She could choose to abort, and I'd be there. Granted, we would have had support from my family and hers, but there are many who do not, and for whom the unplanned birth of a baby might ruin multiple lives (the baby's included).
Admittedly, there is adoption, and in theory, giving up a newborn to adoption might be a best-of-all-worlds scenario (not needing to support the child, the child gets a loving home, the adoptive parents get kids of their own, etc.) But that's all in theory. In practise the adoption programs in Canada and the US are jokes. There are far too many kids in the system, I understand that there are abuses within the fostering system, etc. Couple that with the unique situation in the US where, in many states, gay couples are not allowed to adopt, due to some backwards fear (I am offended by this; any couple who proves they can support a child should be allowed to adopt, regardless of orientation; for further info, read "The Kid" and "The Committment" by Dan Savage). So putting a baby up adoption is not necessarily a reasonable alternative, if there is a chance that they could be stuck in an uncaring "system" for 18 years.
Frankly, the legal discussions on abortion in US law is getting to be a joke. There's that one state that wants to insist that pregnant women wanting an abortion also get a transvaginal ultrasound, insisting that "consent to penetrate is irrelevant, since they already consented to being penetrated when they got pregnant in the first place." I almost threw up when I read that. And then there's Rick Santorum, who thinks that a rape baby is a gift from God. Then there's another state (sorry, I don't remember which) whose anti-abortion laws would also cover spontaneous miscarriage.
In conclusion, it is my opinion that the abortion issue is not about murder, or the life of an unborn baby, but an issue about women's health. Women should be able to make the choice for themselves, in a legal and safe way, to control when and how they give birth.
I would add real quick one important point: outlawing abortion will not eliminate abortion. All it will do is drive it underground (not unlike alcohol prohibition in the 1920s). Women will still get abortions, but it will be unregulated and dangerous. The number of women who get sick or die from having abortions in unlicensd, unregulated, unmaintained facilities will skyrocket.
I'd like to end my post with one quick apology. I forget that we are all united on this board out of only one thing: our love for Star Wars. We all come from different economic, political, religious, etc. backgrounds. I had to remember that when reading the last few pages of posts, because extreme pro-life/no-abortions-for-anyone talk can make me uncomfortable or even a bit offended, just as I'm sure my pro-choice talk may offend some as well. It is not my intention to offend, just as I'm sure it was not anyone else's intention to offend.
"I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain."
-Bene Gesserit Litany Against Fear