Listen: Both the Pro Life and the Biological experts agree that life begins at conception, so what we must look at here is: Is a Fetus Actually a Legal Person?
Well, the 14th Amendment says, "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States." In this case, the word "Born" implies that the baby is already born. I may be wrong But I am using "Citizens" in a broad sense
But if we look back to the biological definition of a living organism, the organism has to 1. Reproduce (although this is moot due to it actually happening at puberty), 2. use and obtain energy independently, and 3. process information. A fetus can't obtain energy independently, nor process information until viability.
Under my philosophy, A fetus is only a developing potential life that is in the grey area of personhood; the more its developed, the clearer it becomes. And when it becomes viable to pain sensation, it is fully a person and must be finished (unless that is, the mother is having an emergency). Even though it is a person at that point, the mother has priority over the fetus in terms of rights, as per a long-standing generic international standard that must be upheld. Therefore, a fetus is a person at Viability and sentience and must not be aborted unless the mother (whose rights trump the fetus') is suffering an emergency that requires the abortion.
This is just my interpretation of the definitions, but I would Love To hear Your Definitions in Detail.