I have been on the Dex twice, only recently coming off the Dex the second time after finding out our unborn daughter was not CAH affected.  Obviously the doctors were able to identify both myself and my husband as carriers and therefore determine if our unborn child was affected or not.    I vaguely remember someone else on this board, I think it was Lisa D, who also had trouble with the doctors not being able to determine if her unborn child had CAH until a few weeks before the child was born.  Fortunately for her the baby was a boy and she was able to come off the Dex early in the pregenancy.  I have always had concern about taking the Dex if the unborn child is not CAH affected, however there were no side effects with my second child as a result of taking dex for about a 10 week period.   I would also have concern for your health if you were required to take the Dex for the length of the pregnancy if was not necessary, so I guess if the CAH diagnosis could be done as soon as possible it would be much better for all concerned.

Good luck.