Cherry picking?

If a couple have a disabled child, it's tragic, but it happens.  The idea of refusing to raise your child or accept any responsibility for it because it is disabled is legally and morally indefensible.  So what if you are incapable of carrying a child yourself, and choose to use a surrogate mother - which means that your fertilised egg is implanted in another woman's womb to be carried to term?  No difference surely? And yet we have a situation where an Australian couple have used a surrogate mother to carry on their behalf what turned out to be twins - a boy and a girl.  The boy was found to have Down's syndrome and a heart defect.  The couple have taken the girl but refused to accept the boy. Their argument seems to be that had the real mother been carrying the children she would have had an abortion on learning of the boy's disabilities, but the surrogate mother who is a Buddhist refused to have one as being against her religion.  Not an easy case, but surrogacy is fraught with potential problems and the phrase which pops unbiddened into my mind is "take one, take 'em all".