@whatlol I don't see the problem with parents telling the kid. I'd think "oh yay I was the sex my parents wanted woot". Then again I'm probably biased because I know my parents wished I was a boy (yeah they told me, no I'm not psychologically scarred, I think its quite funny).
Re: slippery slope argument. I don't see any govt daring to allow embryo selection based on arbitrary traits.
@Yitzi, what about the rights of the child? Some cases of Downs are so serious (like one of the cases in the article, the child can't walk, feed himself etc.) that the child will suffer all his/her life, never able to lead an independent existence, and either dying early or having to be cared for 24/7 by ageing parents. There's a point where aborting the foetus (because it is not a baby at that stage kthx) is an act of mercy. And where keeping it is more a way for the parents to either alleviate guilt or to prove a point rather than acting in the future child's best interests.