I'll voice my opinion simply because -- well, for no reason, honestly. Discussion of the matter is rather useless and never ends up well, because this is one particular area where people never change their opinions no matter what. But I do like to hear myself talk, so off we go.
To me, there are legitimate defenses for abortion and illegitimate ones. Many defenses don't convince me -- the right to privacy, as I mentioned above, or that abortion makes for gender equality. However, we have to take the socioeconomic consequences of abortion seriously. These are what I'll detail here.
Emma
This example is based on the story of a friend of mine from high school. We will call her Emma.
Emma was a competent student, got fine grades, and was admitted to a fine college. However, a few months before her graduation, she became pregnant with twins. Her options were two: to carry the twins to term and devote the next few decades of her life to being a parent, or to abort and continue her life as planned. We should keep in mind that Emma, like the vast majority of people who get abortions, does not really have the resources to raise one child, let alone two.
For Emma, abortion is a choice of no difference. The babies will not be born, not having ever experienced life, and Emma will continue with her life as planned. If she chooses to birth the babies, they will live, but the quality of life of everyone involved -- Emma, her children, her boyfriend, her parents -- will be significantly diminished. The fact of the matter is that if we forced all the people who are considering abortion not to get them, practically every child will be raised in less-than-ideal conditions. We return to the real-life Emma: she did give birth to two healthy children. However, she doesn't work and her boyfriend just lost his job. These two children would be suffering right now if Emma's parents chose not to help with the children (they fortunately did). Is it really ethical to force Emma to raise children if she will ultimately be unable to provide decent living conditions for them? There wouldn't be abortions if everyone who got pregnant was able to raise a child, and you can't justify forcing those unable to raise children to do so.
Let's modify Emma's situation a bit. Let's say she got pregnant as a result of rape. She should be able to abort the children, shouldn't she? If abortion is outlawed, the government is now forcing her to carry children she did not ask for to term, which is grueling in and of itself. Is that ethical? If Emma does not have the resources to raise the children, she can either attempt to raise them anyway or give them up, and, considering that adoption isn't always successful, neither option is very good.
Perhaps Emma's boyfriend chose not to stick around to father the children. Is it ethical to force children into life if they are not going to have a capable family? What if her life is in danger by the pregnancy? Can we really justify bringing two children into the world without parents, when we could have chosen the life of a competent adult who doesn't need anyone taking care of her?
Post-Abolition
Let's say you succeeded in your endeavor. Abortion is now criminalized. What does this world look like?
First of all, there are more children. As mentioned above, more children are now being raised under less-than-ideal conditions.
However, we'll find that there are still abortions. Obviously, some people will still believe that they are entitled to an abortion, and they will go ahead and do it themselves. In the best-case scenario, the abortion will be successful and the woman comes out unscathed. This is ideal and unrealistic. It is more likely that the woman will cripple herself or her child. In a world without safe abortion, more women and children are being hurt than before, even though this was the opposite of our intent.
Let's say Julia lives in the post-abolition world, got pregnant, and aborted her child. If the government finds out about this, what are they supposed to do? Does a fine or jail time really make sense here, when the woman has already been through the psychological torment of unplanned pregnancy and abortion?
If abortion is a crime, attempted abortion is also a crime. Maybe Julia tried to abort her child and failed, and the government found out about it. What's the proper punishment here? A fine doesn't make much sense -- that's just hurting the child unnecessarily. Imprisonment would also hurt the child. How on earth do we ethically punish the attempted aborter?
Conclusion
We notice that my arguments are not conclusive. They aren't meant to be, and no argument on the matter will ever be conclusive. I just mean to point out that it's fine to say "abortion is murder and it should be criminalized", but in reality, things are just not this black and white. If you want to reduce abortions, provide excellent, honest sex education and free contraception -- two things which conservatives, astoundingly, oppose.
I conclude with the words of Bill Clinton: "Abortion should be safe, legal, and rare".