What about a deformed fetus?
If fetuses ought to be considered persons,
then their disabilities would not constitute grounds for killing them. This is why we do not go around euthanizing all deformed and diseased teenagers, even if they are living difficult lives and are a burden on society.1 They are persons, and their right to life has nothing to do with their appearance or health. Similarly, if fetuses are persons, then their deformity is no excuse to kill them. If they are not persons, on the other hand, it should be permissible to kill them regardless of whether or not they’re deformed.