Nobody is arguing that. If the mother is in danger or the child has zero quality of life is one thing. Those are rare cases and usually defects can be detected before the 3rd trimester. What people are upset about would be the cases where a woman in labor decides that it would be 'mentally distressing' to have a baby, they try to abort, it fails, they resuscitate the baby, make it comfortable and after a discussion with doctors and mothers, they kill it. That is legalized infanticide.