We have a daughter with a rare genetic disease, which causes her muscle tissue to dissolve. It turns out that both parents were carriers of a recessive gene defect, without ever noticing anything, so we had 1/4 chance of a disabled child. This has absolutely devastated our lives. For me, the obvious decision "if we had known" would have been to terminate that pregnancy.
She is now 18 years old and an absolute sweetheart, always cheerful and charming - bumbling through her freshman year at college right now. To me, the love for my daughter is perfectly reconcilable with the decision that she would not have lived, had we gotten a prenatal diagnosis. I discussed this once with my wife, who is much more zealous than me, in her devotion to our children (there's another daughter, in perfect health). Especially after the unique experience of gestating this child in her belly, I expected her opinion to be different. To my great surprise, she replied instantly that she would also have opted for abortion.
I could tell you of all the times throughout my daughter's life when she hurt herself in yet another nasty fall, or when she cried because she couldn't join a social experience, simply because of her disability. There's enough pain and suffering in the world, even when everyone at least gets to start out with a healthy body.
Whenever there's a news report about a leap forward in genetic technology, there's always an outcry from the ethics gang, warning against any and all intervention. From first-hand experience, I would love to see a "Gattaca" future happen. Whenever acquaintances announce the joyful news that "they're expecting", I now cringe and silently hope that at least their child will be born healthy. I'm convinced that in some future century, it will be considered an obvious standard of medical care, to guarantee this.