What the law currently says about when personhood begins is irrelevant to a discussion about when the law should say personhood begins.
Also, it sounds like your simply determining this definition of independence arbitrarily. Surely an infant cannot be independent, and requires another person to take care of them. But you want to carve that definition down until it can fit a fetus but not a born child. Sounds like you are just molding the words to fit your opinion without explaining why 'independence' is necessary to be considered a 'person' to begin with.