Let’s do a thought experiment. Let’s say you have a spouse. Let’s say your spouse gets into a terrible, terrible car accident that causes severe brain damage. Your spouse is in a coma. Machines breathe and eat for them. All the best modern medical technology indicates that the only activity in your spouse’s brain is reflexive and not a sign of any ability to think or feel.
So now you have a heart-rendingly difficult decision to make, right? Do you leave them on life support or not? You may feel strongly that one of these answers is right and the other is wrong, but you accept my premise that you are the one with a decision to make. Of course you do. When a person is unable make his or her own medical decisions, the authority to do so devolves to their next-of-kin. The medical proxy is even allowed, in certain situations, to make decisions that can only lead to the patient’s death. Although the question which is the correct choice to make is up for debate, the fact that someone other than the patient must make it is uncontroversial.
Now another experiment. You have terminal leukemia and need a bone marrow transplant soon to save your life. Unfortunately for you, all the potential matches the doctors have found refuse to donate to you for whatever reason. You may disagree, loudly and vehemently, with their decision, but do you have the right to strap them to a table and take their bone marrow? No, of course not.
So we’ve established that those who cannot make their own medical decisions must have someone else make them, that the person who makes those decisions may in some circumstances knowingly cause the patient’s death, and that no one has the right to force someone else to give of their body to contribute to their own health, even if it’s a matter of life and death. In other words, though our Constitution grants us all a right to life, there are acknowledged limits on that right, just as there are acknowledged limits on our right to free speech.
Then I ask you: What difference does it make when a fetus acquires human rights? If it has none until birth, abortion does not violate human rights because there are none to be violated. If it has them at the moment of conception, or at 6 months’ gestation, or when lung development suggests viability, or at any other point in utero, its mother is still its medical proxy and its rights do not extend to forcing her to use her body to maintain its life, so she may decide to abort without violating those rights. In fact, the only potential violation of human rights is to force the pregnant woman to carry the fetus to term. She is the life-support system; she is the potential bone-marrow donor. Not even actual, born people have unconditional rights to these things. Why would a fetus?