Abortion does not necessarily deprive a child of any "experience". Imagine that, as you do the abortion, you save a few cells. Then, from the fetus's DNA, a few years from now, when the mother is ready, you recreate it and install it in her womb. Since a person is defined by his or her DNA and life experiences, the latter of which a fetus lacks (don't even try), it ensues that the chance for a person to experience life is only irremediably lost if his or her DNA cannot be retrieved and/or he or she is old enough to have experiences that cannot be reproduced.
Now imagine that scans have shown with near certainty that your child will be severely disabled. The best solution, from everybody's point of view, would be to save its DNA and abort it. Then, once it is possible to cure the disability and that cloning is a mature science, you remake the exact same child, allowing him to experience a better life.
Or you could just abort the child and make a new, different one, who has no major disabilities. It's good (though mostly irrational) to value life to some extent, but let's not get ridiculous. After a few weeks of pregnancy, there is nothing about the fetus that could possibly justify considering it human. Whether it will turn into a human later on is wholly irrelevant, especially if you make another one to replace it. As long as the fetus doesn't have distinctive human characteristics, the decision to terminate it has nothing to do with morals. It's just a medical procedure.
kholdstaire: there are no "laws of nature". What you call laws of nature is just how most animal species work, not how they should work. Evolution/natural selection can't really do much for us anymore, since we're progressively inventing technology that makes the process obsolete.
Glen: there is no line. It's like when you have a small pile of sand versus a big pile of sand. You can definitely tell that some piles are small and some piles are big, but in between it's a big mess of "eh, I don't know, it's kinda big but not big", etc. Same here. There are cases where the handicap is obviously big enough, others where it's obvious there's no handicap. But there's no line in between. It's just completely subjective. You might want to err on the side of caution, though. Also, if you want to know where _I_ draw the line, well, if there was a way to calculate the odds to have a much better child if I made a new one, and they were high (like 95%) I would totally push for it. Ultimately, though, it's the mother's choice and I don't think she'd be very fond of doing abort/retry unless the situation is really bad.