From a speech to the California Republican League on September 26, 1998 by Reverend Ann Hayman:
“What are our deepest values? How do we feel about an ideological shift that makes a fetus a patient and a person? Nowhere in Scripture either Hebrew or Christian are any such claims made.”
Because they tended to use the same terms for pre-born and post-born children, it probably just didn’t occur to the Bible writers to spell out who and what they were in relation to everyone else (except special cases like Exodus 21 addressing in-utero injury by a careless third party). :/