In Ireland, a brain-dead pregnant woman's body is being kept on an incubator so as to make the fetus turn into a baby born motherless.

A dead body on an incubator is not a human being, and has no rights. A fetus of 17 weeks is not a human being, and directly has no rights, but causing it to develop into a human being in disadvantaged circumstances would be harm or cruelty to that human being. That's what Ireland is trying to do here.