As I said in another comment: that’s simply not your decision to make. You’re neither qualified nor entitled to their private life; the fact that the particulars revealed to you in this instance meet your standard does not mean anything.
And no, our laws are not based on that fundamental principle. The US legal system is built on the English system, which emphasizes autonomy in the forms of property, self-legislation, and all of those other things that actually appear in our foundational documents.
I’ll say it: the mother’s rights trump those of the fetus when they conflict.
If we accept the right of bodily autonomy then the fetus has no right to the mother’s blood and sustenance.
If the state denies pregnant women bodily autonomy then it must assume the responsibility to care for them. Stats that ban abortion should cover all costs of pregnancy, at minimum.
The laws are based on a moral code that protect the most vulnerable.