Many of the founders, including the father of the Constitution, James Madison, opposed the addition of a Bill of Rights, for the simple reason that they feared that to begin to delineate rights might infer that the people's rights were confined only to those that were listed.
They lost that political debate and were forced as the first act of the new Congress to set in motion the amendment of the Constitution to add a Bill of Rights.
But they were careful to add the Ninth Amendment, which says:
The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.
You see, they well understood that the God-given rights of the people, starting with the right to life, precede and supersede any human constitution or written law.
They understood that the right to life is unalienable.
Unalienable:
incapable of being alienated, surrendered, or transferred
And so, even if you want to ignore the explicit, imperative requirements of the Fifth and the Fourteenth Amendments, abortion is, and always has been, completely illegitimate and unlawful.
This is why I always am careful to say that abortion violates God's law, the natural law, the natural law moral principles of the Declaration of Independence, every stated purpose of the U.S. Constitution, and that document's explicit, imperative requirements, which are binding on every single officer of government in America, in every branch, and at every level.
Then you're asking me to accept the premise that the people who wrote and ratified the Fifth, Ninth, and Fourteenth amendments intended for it to outlaw the practice of abortion, and then forgot to do it.
How dumb do you think they were?