First of all I want to welcome you to the board and say congrats!!
For me personally I had the NTS screening with the blood tests first. I wanted to avoid any invasive tests if I could, no matter how small the risk was.
Loving Mom to three
Loving Mom to three rambunctious
I had the NT test and the first trimester bloodwork screening. My bloodwork came back 1:20 chance of ds-which needless to say, scared the crap out of me! (BTW everything turned out normal in the end)
At the time I got my results I was 12 weeks. I had the choice to have CVS or Amnio (or nothing). After speaking with the genetic counselor, I chose to have amnio-which I had to wait 3 1/2 LONG weeks for. CVS I could have had sooner, but the risk wasn't worth it to me.
The reason I chose Amnio over CVS was because of the miscarriage rates. There are "standard" miscarriage rates for both tests, however the standard varies by where you get the tests done. For example the clinic where I had my amnio done had a 1:1000 average. However, according to my genetic counselor, no clinic can get a better than 1:300 ( i do not know the accuracy of that statement) for CVS.
During my wait I did ALOT of research, joined alot of chat rooms/forums and discovered there are a TON of false positives from the First trimester bloodwork.
If I had to do it all over again, I would opt for the NT u/s and the 20 week u/s followed by amnio if any problems were indicated. Personally I think the bloodwork is unreliable and apt to cause alot of unnecessary stress.