I don’t believe you need to look to the 14th Amendment in order to protect those that haven’t passed through the birth canal yet. The Fifth Amendment provides that “no person” shall be deprived of “life, liberty, or property, without due process of law.” If the SCOTUS (or even a federal law) were to recognize the personhood of the unborn, then that would be enough.
That may just protect a person from government funded abortion, as amendments are restraints on what the federal government can do. Not sure it would cover privately funded businesses, etc.
The 5th Amendment would not be sufficient. At the time it was adopted you had groups of people who were born and lived their entire lives without any rights whatsoever. The 14th Amendment was added to the Constitution because the 5th had clearly been inadequate.