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.
Emma sounds like a commonsensical girl. I'm sure that she very well knew that having sex, even if "protected", always carried the possibility, in principle, of leading to impregnation. By having sex, Emma invited the possibility of getting pregnant. She wasn't raped, nor was she forced to become pregnant. She understood, then, that by having sex, she risked putting all of her future plans -- however admirable they would be -- into jeopardy. Why think, then, that Emma is in any way justified in ending two lives which she herself invited into existence?
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
So is one justified in ending a life based on one's own subjective judgment of what a less-than-ideal life would be? Imagine what that would entail: one would be justified in ending another's life if they ever come to decide that another's life is less-than-ideal or that their death would be preferable to their continued existence. Suppose you wake up one day in the slums of Mumbai (or wherever) without a house, without food, without clothes, and without any of the possessions you own now. Pretend that in the days that come, your life is reduced to the most dirty, poor and arduous existence imaginable as every day becomes a battle to find enough food to survive. Regardless of whether you would like to continue living, which I'd bet you'd still want to in some way, wouldn't it be extremely presumptuous of me to decide to end your life because I deem it too "less-than-ideal" or if I deem that you would prefer death rather than the life you live now?
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.
Before anything, it should be mentioned that pregnancies that result from rape tend to be low due to the inherent violent nature of rape. That said, why should she be justified in ending the life of a child who is not responsible for the crime that has been perpetrated against her? Why not put the child up for abortion? Sure, she's in a terrible situation, but one can only add to the immorality of the situation by ending a life. And, again, isn't it preposterously presumptuous to abort a child because of one's subjective beliefs regarding its possible future?
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?
Unfortunate, again, but Emma knew what she was risking when she decided to have sex. And, again, adoption is an option. Perhaps only if her life is in extreme and legitimate danger would the use of abortion be considered permissible at the mother's thoughtful request.
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.
No reason to justify abortion as explained.
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.
I'm not completely opposed to abortion as long as it used as a method of last resort to save the life of a woman who faces critical and legitimate danger in giving birth. To use it as birth control is nothing but a selfish and immeasurably cruel action of "convenience" to escape the responsibility of an action that was consented to in knowledge of its potential results.
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?
As I have said, I haven't considered what authoritative or legal action, if any, should be taken if an abortion occurs in a country which has criminalized / banned it. I'll reserve judgment in the meanwhile here.
I conclude with the words of Bill Clinton: "Abortion should be safe, legal, and rare".
With over 1.3 million abortions per year in the US, I'd say that it has unfortunately become the opposite of rare these days.