It's a horrible situation but why does the baby have to die rather than being put up for adoption?
Why should society reward rapists by allowing them to forcibly breed? The law typically does not allow one to benefit from his wrongful actions.
Why should a raped woman, or a raped man, be forced into slavery or involuntary servitude, in violation of the 13th Amendment, by being required, in the former case, to carry the rapist's spawn to term and, in the latter case, to pay the rapist to support her spawn?