Being partly disabled, I’d never, EVER wish such a condition on anyone, much less my own flesh and blood.
If these parents want to “choose” such a state for their children, then let it be their choice to foot the bill for the advanced care and education required over the kid’s lifetime — it’s a much easier “choice” if you know someone else will be taking care of things...
On the other side though, a child should not be discarded because of a disability. I would not want to see parents told that they will be denied any assistance if they don’t abort a child that is mentally or physically challenged.