Congrats!  I did choose to take Dexamethisone because our first child was born with ambiguous genitalia and required a rather long surgery(10 hrs) as well as a couple short ones. You do need to start the dex treatment very early into the pregnancy to gain the full benefits of the treatment. I started at 4 wks. We had an ultrasound done at 6 1/2 wks to establish exact timing so we could have a CVS done rather than wait the couple extra weeks for the amnio. We found out then we were having twins! We did have to wait to have an amnio.

The side effects while mildly unpleasant were worth it for the possible benefit of no surgery or little. They were basically PMS times 100! Moodiness, weight gain, acne... I had to be weaned off slowly when we got the amnio results. Our boy is a carrier and our girl is unaffected. Coming off was worse than actually taking the stuff. Check out the debate board for there are some who disagree with taking it but after our experiences with our first I would not not take it.

PS  the "twins" ( I hate the term) are now 3 yrs old. They are perfectly healthy, happy and normally developing.

Hope that helps. Good luck! Feel free to email if you need to chat further