You should begin taking the Dex immediately. I was started at 5 weeks. You need to speak to your doctor/ob. I asked my daughters (she is SWCAH) endo what I needed to do and went from there.

True, you don’t have to take the dex, but if it were to turn out you were having a baby girl you might want to. It’s up to you. You need to get with a Genetic Counselor, she/he will help you through everything you need to know.

Yes, the dose is based on your prepregnancy weight. I took dex for 2 months until the genetic testing (through a CVS) came back saying I was having a boy. 

Keep in mind, if you do take it, and find out you are having a boy you will be able to discontinue taking the dex. But you will have side effects. I had bad headaches for about 1-2 weeks, then it was overwith. You will also have to wean yourself off the Dex gradually.  

Sherry