Did the Founders intend to protect unborn children as "persons" who would be subject to Constitional protections? That would have to be answered before you could make that argument.
I don't think that would have to be answered at all -- for the same reason that issues like cloning and euthanasia could still be addressed in Constitutional terms even though the Founders had nothing to say about these issues. Modern medicine, science, and technology has introduced a whole array of issues into our national politics that never came up in the 18th century simply because they didn't exist back then.
Black Americans today are entitled to full Constitutional protections even though the Founders specifically did not intend to protect them as "persons" under the Constitution.
Of course they did.
Abortion was universally considered an abomination in the late 1700s.
Strong criminal penalties for such a vicious act were on the books in every state's legal system.
The burden is on the fools who would deny that the Founders intended such a protection.
The right of all humans, born and unborn, to life comes from God, not from our founders. They acknowledged and expounded our preexisting rights given to us by our Creator.
wrong question
Rather, did the "inalienable rights to life, liberty and the pursuit...." (yeah, I know, wrong doc) envision a world view predicated on the individual having those rights due to a particular view of the world, man, and a Creator? In other words, our Constitution views the the law as a natural unfolding of the RIGHTS of the individual over the state, and the consequent rights of the state. I believe the Constitution sits on a foundation of a view of DERIVED rights, and not mere stipulated rights. If that is the case, then the basis for your answer is clear, it is just a matter of how we get there. If you try and hammer our modern post-Christian view back to 1789 to "make it work" in todays unbelieving world (tip of the hat to John Adams) then the answer is "I dunno" and the best we can do is advocate a state by state situation. That is my strategy as I think it is hard to argue that most of America will buy into a solid pro-life position. It is too "religious" for them.
By the way this comes from someone who helped form one of the first Metro Right to Life groups, studied under Francis Schaeffer when the majority of the Protestant world was asleep at the switch on the issue, has led abortion protests at clinics, had personal conversations with Joe Scheidler, and been interviewed on a number of local media outlets as a "spokesperson" for the pro life position. I am not a shrinking violet on the position, and I was a vocal advocate before most of the protestant church even knew it was an issue.