As a follow up to the dolphins rights post this morning, Australian ethicists argue that after-birth abortions are a logical extension of pre-birth abortions because there's no moral distinction between the fetus and a newborn. This is what happens when you define personhood functionally and assign rights that way. There is a logical slippery slope that is no fallacy and this is it.
They're correct that the short trip down the birth canal makes no moral distinction. (See the SLED test.) Sadly, rather than realizing this logically means we should protect the unborn's rights, they don't question their premises and take the logic the other direction.