But fetuses are not potential persons but persons with potential.

Define a person. What distinguishes a person from 1) a plant, 2) other sapient or sentient animals, and 3) a complex robot?

In early stages of a pregnancy, the zygote (or whatever) has no will of its own. Philosophically, it is not a moral agent. In the moment, it has no moral value.

If you consider potential to become a person, to itself be a morally valuable thing worth saving, a critically important question comes up: why do you not promote rape? Every second a woman isn't pregnant, a potential to become a person is wasted. Every ejaculate from a man is millions of potentials wasted.