My husband and I knew we were carriers because our first born has CAH. When I became pregnant with my second child they did a chorionic villi sampling (kind of like amnio) I think this test can be done sooner than the amnio though. Chorionic villi sampling (cvs) will tell you the gender of fetus and whether they have CAH, are a carrier (good to know for when baby grows up and wants to have children) or if they are not affected at all. If fetus is female and a carrier there are medications mom can take during pregnancy to lessen the risk of ambiguous genitalia. I was started on dexamethazone prior to getting results back from the test which took about 3 weeks. My daughter is just a carrier so I discontinued the use of dex.