Every reference in the Constitution to individulals that I can find starts from birth - from the calculation of a person's age for purposes of military service or holding public office to questions of country of citizenship. All predicated on time or place of birth. They made no reference to time or place of conception, and make no recognition of the person before birth.
If there's any reference there to recognition of "personhood" prior to birth, I'll be happy to consider it if you can show me where it is.
The Fourteenth Amendment, in its Article One, makes a clear distinction, in two separate clauses, between the privileges and immunities of citizens, which commence at birth, and the rights of all PERSONS, starting with the right to life. The two groups of persons are treated separately, necessarily.
All citizens are persons. All persons are not citizens. But the latter’s God-given rights are guaranteed equally within every jurisdiction nonetheless.
Citizenship begins at birth. Personhood does not. It’s self-evident.