"So, for everyone saying they wouldn't risk miscarriage and have an amnio, I think the question still stands, would you find out if it was just part of
all those blood tests that you have early on in pregnancy?" No. I wouldn't abort for ds so no point in having tests imho.
And where is all this evidence that "most babies with ds die before term."?
I think it's fair to say that it is believed that many miscarriages before twelve weeks happen due to perceived chromosomal abnormalities, but this does not mean that this is due to downs syndrome. We do, after all, have 46 chromosomes - any one of those could have an "abnormality" 
What people also fail to see is that for every baby with downs that is detected through amnio, three "healthy" babies die as result of miscarriage because of the test.
Testing creates a false sense of security IMO, and this is the reason why so many people bring up the fact that there are so many other conditions that cannot be tested for. How many people have posted on here after their amnio saying that the baby is absolutely fine. The reality is that they don't know that; they know that the baby doesn't have downs or edwards or whatever the other conditions are they test for in amnio, but they don't know that the baby won't have complications at birth and develop cp, or be autistic and won't show as having anything wrong until it's two or three, or be developmentally delayed for any number of other reasons. A clear amnio result is held up far too readily as a guarantee of the "perfect" baby, when actually it guarantees nothing of the sort, and gives parents a false sense of security.
I wonder how many parents that have amnio, with a view to terminate if the results come back positive for downs, end up with a child with a different disability they were not prepared for.
As for the "pro choice" argument, the difference is that when aborting a baby with downs that baby goes from being wanted to discarded in the space of a test result. A much wanted, anticipated baby suddenly becomes disposable when it turns out not to be what they ordered.
I am not referring here to babies that have conditions that are incompatible with life such as anencephaly, as that is a totally different issue.