http://pedsendo.med.cornell.edu/cah/factshet.htm

Here is the web site from Dr. Maria New’s web site for DNA testing for CAH.  I had it done and my insurance paid for it.  It is a blood test. They must take blood from the mother, father and child.  I did when I was pregnant with our second child. Our first child was a boy with CAH (salt wasting).  I took the dex treatment. Our second child was a girl with CAH. The dex treatment worked and she was not virilized.  I lived in Washington DC.  The blood was taken locally and sent to Dr. Maria New. Any lab or hospital lab can take the blood and have it send to Dr. Maria New.

I had amnio at 17 weeks.  Our third and fourth pregancies were boys - one with CAH and one without CAH.  I had CVS done at 10 weeks.  The CVS was much faster. I was able to stop the dex because you do not need dex with a boy.