Paul.  There are no drugs your wife can take to ensure your next child does not get CAH.  As you and your wife are both carriers of the condition, there is a 1:4 chance that any child you have together would present with the condition.  However, to try and prevent virilisation of a female affected child, there is now the option of taking dexamethasone treatment during pregnancy, which may save your daughter from needing surgery (although this is by no means guaranteed!). I am sure others will post articles for you to read on the subject, which will no doubt help you but I would advise you to talk to your son’s endocrinologist who may suggest a referal to a genetic counsellor, so your options can be discussed in detail, as you will also need DNA tests (assuming these haven’t already been done?).  Good luck!