If I understand it right, there’s one person there until separation is possible. Then there’s two.
I think it’s called “viability”.
When there’s two, the “new” becomes a ward of the state with a mother having first dibs on guardianship.
That’s how I see it anyway and I think it’s more or less Roe v Wade in a nutshell.
It’s blurry when there’s complications. That’s another thing.