That’s not a good argument, nor true.
A foetus is the stage after the embryo, when organogenesis is done meaning tissue and organs have formed, right up to the point of delivery.
This means at delivery, a foetus becomes a baby by coming out, no other changes.
So i wouldn’t really call that difference relevant in a moral debate. The stages of development or number of weeks is, but you can’t really distinguish the two without this specification.
That’s why where i live we allow 14 weeks after the first absence of periods for example.
Edit : I don’t know why i got downvoted, i’d love to hear why i’m wrong. Maybe just to be clear, i agree with abortion, just not this argument.