Sorry, I didn't read your thread title properly.
I'd like to say don't worry, but you will, and my heart goes out to you. There are more tests that they can do. I went for a CVS because it was more immediate, although the risks were higher. An Amnio can be done from about 18 weeks.
I don't know what tests they do now, I had a blood test with DS1 7 years ago, nuchal folds for the next 3, and DD2 had a 1:5 risk of DS, 1:17 of another chromosonal disorder. The chromosonal tests came back OK, we had to have a full scan to make sure there were no organ defects.
So, despite the high risks, my little girl (now 14 months old) was just fine.
I would say that this was before I had discovered MN. Since then I've learnt a whole lot more about DS, and my knee-jerk reaction then would be very different to how I would react to the same news now. I suspect your mind is racing and you are having a panic, but sit tight and breath deeply until you know more. Good luck, let us know how you get on.