I think in the cases of childre born without parts of their brain.. (google searches for the correct term)..
anencephaly or other fatal non-cureable conditions, that euthenasia should be discussedd between the mother/parents and the doctors, taking into account the religious and moral beliefs of the parent(s) and the outlook of the child's life in regards to health and pain/suffering.
No matter what your position on this issue is- you have to admit that this has to be extremely emotional and stressful on the parents and to some extent the doctors of these children.