The prepare for the worst but hope for the best definently applies. I didn't even know what cf was before my son. But know until they say he has it, don't be too worried. My sister has a 2 year old who can't gain weight if his life depends on it. And he also has constipation problems. They have run every test and can't find anything. He is on the verge of getting a feeding tube. So of course they tested him (especially being my nephew) and it was negative.