Interesting thought, but consider the implication. . .using your logic, the child can be killed post-birth because the child is the result of an ongoing assault. Sins of the father onto the son kind of thing.
“using your logic, the child can be killed post-birth because the child is the result of an ongoing assault”
Nope, once the child is born the assault has ended. The woman would also not be justified in killing the rapist after the fact.