Before we go further down this rabbit hole, there are two points to make about the constitution and the society that created and evolved with it.
First, it recognizes that, even though we are all persons, not all persons are entitled to the same rights. To me that says that, even if we consider a fertilized egg to be a person, we are not required by the constitution to treat it the same as an adult.
You are entitled to be wrong in your opinions.
I'm going to roll with the mindset of Supreme Court Justice Potter Stweart and the pro abort lawyer (Sarah Weddington) and their take on it.
Secondly, the 14th amendment of the constitution seems to imply that until you are born you are not a citizen and don't get the protections of a citizen. What protections you do get before birth, if any, are not mentioned.
The 14th clearly says that "all persons are entitled to the equal protections of our laws." Be they citizens or not.
Your lack of comprehension not withstanding.