Don't know but

I believe you are fairly young so I might opt for a NT and then an amnio if you want more of a definitive answer. The Drs in my area(Boston) were not too big on doing a cvs at all. They thought I was crazy to consider it if there weren't any indicators there could be a problem. It is stressful to wait 4-5 weeks more but the risks with amnio are so much better. I was even worried durimg the amnio when I saw the needle coming sort of close to my baby's bobbing head as she slept. Then I got nervous about making sure the pin hole sealed up properly and that there wouldn't be any contractions after the amnio etc.

It is so hard to say what is right for you.