They do genetic testing from the amnio-  they compare the father’s and mother’s and baby’s DNA to see if the baby is a carrier or has CAH-  the baby needs to have the the recessive gene from both parents.  So the Dad will give a bad gene ( because he has two bad ones) and the mother has on good gene and one bad gene-  anyway that will give the baby a 50% of having CAH,  but will at least be a carrier.  It might be wise for your friends to see a genetic counselor? 

 

Good luck.