It is better to overmedicate a newborn for a short period than to not medicate an adrenal insufficient baby.  In my opinion, your endo is right to want to continue with the meds and see how his levels are in March.  At that point they can also look at other steroids like the delta 4s (androestendione) , and do an ACTH stimulation test.  They can also take more blood for a genetic testing done on him.  Since they already know which mutation to expect, it is a very easy to do.  If he doesn’t need the hydrocortisone or is on too much, by then he would have big chubby cheeks and the beginnings of a cushingoid face.  It is always good to question why a Dr. is taking a particular approach but I think in this case if he doesn’t have CAH, he hasn’t been on meds for too long and  he will be weaned off the meds and all will be OK, and if he does, then you are glad that you started him early.  Any possible side effects from the unnecessary hydrocortisone in short term beats not having enough cortisol.  God bless and keep us posted.