Had they known about the measles and the associated risks to the fetus, they could have aborted, waited a few months, and then started another pregnancy that would probably have resulted in a healthy baby. The correct diagnosis, after all, would have led to an outcome in which he did not exist. The very idea of judging one's life better or worse than nonexistence strikes some philosophers as absurd. Others, like Derek Parfit, contend that it at least makes sense to say of a life that it is worth living or not worth living. Yet even Parfit shrinks from the implication that a person whose life is not worth living would have been better off if he or she had never existed.
Some people feel that any kind of life, no matter how awful, is better than nothing.
If every life is worth living, then it can never be wrong to bring a child into the world, no matter how painful that child's life might be. But most of us feel that it would be wrong knowingly to conceive a truly miserable child. Surely, one has a duty not to bring such children into the world deliberately. Consider a couple who know that if they have a child, he or she will likely have a happy life. Most of us would say no.