Is there a natural right to abortion? What are rights? A right is a valid claim that you have against the whole world (or most of it at least). "Natural" alludes to the fact that it comes from Nature. Therefore, the natural right to abortion is a natural, valid claim to abortion that one has against the whole world (or at least most of it).
A man and woman procreate. If it is willed, their act will result in a "cluster of cells". Are we all not a cluster of cells? If this is true, would I have the right to kill a man? After all, he's just a cluster of cells. Would I have the right to kill a cat? They are just a cluster of cells. Or a dog? They are just a cluster of cells. Could one have the right to kill a fetus?
Let me give an example. You see a little boy on the street. You invite him in, hoping to give him a better life. At first, it's comfortable. You clothe them and feed them, and they grow under your care. One day, the boy pulls a knife on his keeper. "Your money or your life", he says. Many years have gone by and your love for him has grown. Do you lay down your life? Or do you kill him? You kill him.
Was that right? Did you have the right? Of course, do you not have a right to life? The boy also has a right to life, but who has a better claim to his life when he threatens another's life? The aggressor or the aggressed? The aggressed. They don't have to exercise that right. But you do. Are you a murderer?
There is a man and a woman. They love each other very much. They want to start a family. The woman is pregnant. There is pain and suffering, but the reward is worth it, she feels. Eight months in, they visit the doctor. He tells them that they have two options: the mother or the child. There are no other options. What would you choose?
Is there a correct answer? There may be a better answer. There may even be better options. Only He Knows.
If a fetus is not "life", when does it become life? Is it life all along? If it becomes life, would one not have a better claim to killing it after it becomes life then before? The latter is as if one unsheathes a pencil. It can be deadly. The former is like a hidden bomb. No one is the wiser until it destroys. Or maybe not. Only He Knows.
You fall on hard times. Is it right to kill your children? Less mouths to feed. Theoretically, they can become a threat to your life one day. Sophistry. Do you have the right? No. What is your intent? It better be right. It may never be right.