I am pro choice with ONE caveat. If the father does not want the baby, then the mother has to either abort or support the child on her own. The woman must be made EQUALLY responsible for the pregnancy (except in the case of rape and incest).

Currently, the woman has no responsibility for the pregnancy. She can either have an abortion, against the father's wishes, OR she can force him to pay 18 years of child support. She's in the driver's seat. She makes ALL of the decisions. Including the decision to have unprotected sex.

If someone is a strict constructionist who interprets the Constitution word for word, the sanction for abortion is given under the Fourteenth Amendment.

The Fourteenth Amendment of our U.S. Constitution defines a citizen “a citizen” at birth. If a woman is carrying a fetus in the womb, the U.S. Constitution does not designate the fetus as “a citizen.” It would take an amendment to the U.S. Constitution to declare a fetus a citizen. You have to be born in order to be recognized as a citizen. Therefore, a woman does have the right to choose. A fetus inside the womb is not designated as a citizen according to the U.S. Constitution so by default is not entitled to life, liberty, or prosperity. You have to be born in order to be endowed with those privileges. To conclude, neither the Federal government nor any of the States can deny a woman the right to choose.

If abortion is murder, abortion would have been terminated years ago due to the cruel and unusual punishment clause under the Eighth Amendment. Again, proof that a fetus is not recognized as a citizen of the United States of America.

To be clear from the offset: I do not identify as "pro-choice". I support legalized abortion. I think the development of the "pro-choice" and "pro-life" language was a strategic innovation that has more to do with asserting moral superiority than it does with actually having productive conversation or resolving the issue. That said...

The disagreement is fundamentally one of designation; where do we determine that human life actually starts? The tricky thing is that there truly is no objective, absolute answer. I arrive at my own conclusion differently than most people, but more on that in a bit.

Most anti-abortionists designate the start of human life at conception or very shortly thereafter. They view the fetus as a living human being and believe it should have the same rights as any other living human being. To them, abortion is taking the life of a human being, at best to save someone else (which would be ethically dubious to most people in other circumstances) and at worst to avoid an inconvenience. To them the decision is clear: the life of another person who is at no personal fault cannot be sacrificed to save someone else.

Most pro-abortionists designate the start of human life sometime after conception, though notably most still place it before birth. The designation tends to be made around the time when the fetus would be considered viable and/or capable of feeling pain; pro-abortionists and anti-abortionists are actually somewhat similar here in that at some point in the pregnancy both generally think that it is wrong to hurt the fetus/baby to benefit or prevent harm to the pregnant party. However, for pro-abortionists because life does not start at conception there is no conflicting rights issue with earlier term abortions. It is not wrong for the pregnant party to place their concerns for personal safety, financial security, career prospects, or anything else over the non-existent interests of the fetus.

Personally, I am a pro-abortionist but also understand the matter in terms of social and evolutionary practicalities. Abortion is as hold as humanity itself and not unique to our species. It has and still does perform multiple positive functions for us as a social species, predominantly with regards to social and familial matters.

Tangentially... I find it interesting that while most anti-abortionists think that the fetus is a living human from the moment of conception most do not appear to advocate the death penalty or even life in prison for people who get abortions. Most are opposed to legalized abortions but very few seem to have any strong or coherent views on what the punishment should be for a person who seeks or receives an illegal abortion. Arguably, that indicates even they do not view the fetus as equitably alive and human (unless they categorically oppose those punishments and also have barely formed views on punishment for murder in general, which is statistically quite unlikely).