Interesting that throughout this whole thread, and it seems the campaign (did a bit of googling), no-one has mentioned the Abortion Bill currently going through parliament to allow terminations beyond 24 weeks. Regardless of result. So, should it reach completion, there won't be any discrimination/special treatment (negative/positive depending on your personal view!!!). So long as it's consensual.
I think, at the end of the day, if the natural outcome of a pregnancy is not wanted by the person carrying it, then forcing the pregnancy to continue is not going to have a positive outcome.
Neurotypical or otherwise, having babies is a choice that the adults have to make on behalf of a child before it exists. You can't get around how selfish an act it is. People know what they can cope with, and sure it would be ideal if everyone who was TTC was prepared for a set of DS triplets, because then the outcome wouldn't matter, realistically... people tend to bank on having one, neurotypical child. Sometimes that's all they can manage and that's not something to be judged on.
It's also important to remember that not everyone who is allowed to terminate, terminates. Not everyone who is encouraged by doctors to terminate, terminates! Termination is never an easy choice, and there are always emotional examples of how this law change might negatively impact people.
Just look at the "wrongful life" cases! You just don't know everything that can happen, how that pregnancy can turn out, for certain. You do your best, you trust the experts. Sometimes that means knowing you couldn't cope, and either terminating or arranging for adoption at birth.