If the fetus is indeed human, the 14th Amendment requires the federal government to act to prevent the deprivation of life without due process.
The 14th Amendment also requires the federal government to have its own definition of what a person is, so, even though that definition was done incorrectly in Roe v. Wade, the federal government will, indeed, determine the legality of abortion nationally.
It's not as absurd an idea as we once would have thought. In today's political climate, there is no "reason" to anything. This could very well come to pass.