We opted for the amnio for several reasons: as Tonia said, the CVS is more invasive, so the risk of miscarriage is higher - it's still not very high, but moreso than the amnio; we had tried for 9 yrs to get pregnant, and I wasn't about to take any unnecessary risks! As far as we could tell, the only advantages to the CVS over the amnio was earlier detection (I think it was about 5 weeks earlier); this was presented to us with the knowledge that earlier detection is better if you are considering abortion if the baby is affected - that was NOT an option for us! For us, these factors just did not justify the extra risk; if you were extremely sick from the dex, I guess an extra 5 weeks could seem like an eternity, but I opted to "stick it out", and am glad I did! Good luck!