In many American states it is legal to screen and select on the basis of sex, for non-medical reasons. In fact, a 2006 study (see below) found that 9% of [preimplanation genetic diagnosis] procedures carried out in [in-vitro fertilization] clinics in the U.S. were performed for this reason. Other reasons include screening for an embryo with the same immune type (“HLA type”) as a current child who is ill and requires a transplant of some sort. Screening for these “savior siblings” was done in 1% of PGD procedures. And 3% used it for a reason I personally find jarring – to specifically select embryos with a mutation causing a genetic condition. This is usually in cases where both parents have either deafness or dwarfism and they want their child to be similarly affected. This gets into the political movement objecting to society labelling conditions as “disabilities”. I can sympathise with that to some degree – more for some conditions than others – but I think, if it were my child, I would still rather he or she could hear.
That's Kevin Mitchell, discussing GATTACA, an entertaining sci-fi movie with a respectable 7.8 imdb rating. Spoiler alert, the premise of the movie is that at some point in the future there will be strong stratification of people into two classes, the "valids" and the "invalids", based on whether they had healthy traits selected for via preimplanation genetic diagnosis.
It seems to me highly unlikely (<0.01%) that a nightmare scenario of this sort would actually occur. One of the main reasons is because of the large plurality of values among parents, as seen above. A prevailing reason people have kids is to propagate a form of themselves into the future, and in many ways it defeats the purpose when you select against certain traits or even perform some sort of genetic engineering.
The other reason is something we know now better than we did 15 years ago, when GATTACA was released. And that is that DNA doesn't actually explain all that much of physiology and behavior--there are also strong epigenetic effects as well as stochastic effects of gene expression.