Having “rights” requires sentience. Only human beings have rights. Animals don’t have rights (though people have a moral obligation to treat them humanely). Human zygotes, blastulas, and embryos likewise have no rights because there is no humanity and no sentience.
The case of a 3rd-trimester fetus is more ambiguous because by 30 weeks or so, the fetus has a functioning cerebral cortex (which continues to develop after birth) & is thought to be able to feel pain. By “feel” I mean experience negative human emotions—not simply demonstrate avoidance behavior, which even microscopic invertebrates can do.
So ethically there is room for debate on whether the fetus achieves “rights”—including the right to life— in its last weeks of brain development versus not until birth. Surviving birth is a stronger requirement, but viability outside the womb is blurred today by high-tech hospital care. Proponents of euthanasia for severely handicapped newborns would move the “rights” line to some time after birth. I think these are all valid points for ethical debate.
Declaring that rights magically appear as some sort of religious “emplacement of the soul” into the zygote at the moment of conception is uninformed delusional fantasy. It is not a valid point for ethical debate, even if a popular belief. There are no scientific approaches to resolving the issue.
Being a “potential” human only confers “potential” rights!
The question is loaded (sorry @maxlynn) because the phrase “unborn children” is an oxymoron to all but the most ardent right-to-lifers. The question presupposes the answer: Real children have rights.