I would have a second look at it from another doctor (so I'm not insta-killing a baby) then yes. Without a doubt. The kid would be aborted if it had Down Syndrome.
I would not have the responsibility nor know-how to take care of a kid with Down Syndrome. If some anti-abortionist group attacked me and made my family keep the child, I would give it up for adoption. It's one thing to have a kid with a disability like that, it's another to know if you're capable of taking it on. I wouldn't be.
That and it ruins the quality of life for everyone, including the kid. My neighbor has a teenager with D.S. Every single freaking morning she sits in the driveway and screams nonstop about how she doesn't want to go to school. I mean, she can't even speak. Just screams. Sometimes it doesn't even sound human. I thought someone had hit a dog one time towards the beginning of it. And the entire neighborhood is annoyed by it. Wakes me up once in a while. It's clear that her impact is really taxing on her parents, especially the father who has to stay at home all day to take care of her. They can never go on vacations or get leave of the kid, and she'll never leave that small tight environment outside of repeatedly going to school (or day care) during the day.
And that's one of many examples I can give. I'm also around DownSyndrome kids at a horse ranch I volunteer at. They aren't as bad, though they do lose it every time, sit on the ground, and throw a screaming tantrum about not wanting to go up on the horses.
edit - random fixes.