The cynic in me says, the fetus has great value to the cosmetics industry whereas the person with a fatal disease only has a future as soap (soylent green?)...
On a more serious note, why are you so dead set on attributing a "value" to a fetus. For all I know, the fetus is part of the mother, being physically part of her body (through that cable thing which I can neither spell nor pronounce in english), very much the same way as a mothers hand is attached to her shoulder through her arm. Once they get "seperated", yes, then they are two different beings. Well, just one point of view