gavra_at_work,
Interesting theory and not implausible. I would expect there to be a source in Rishonim or Achronim as such (Rodef = person), and invite the Olam to help out with finding such a source.
I think in this case context is a better guide than a concordance. These halachos don’t happen in a vacuum, and all of the surrounding halachos are talking about human rodfim. If the fetus did not have at least some aspect of personhood, why would we need it to have the status of rodef at all?