i am so sorry for your loss. my thoughts are with you.
you don't know the strength you have sometimes till you are in the situation. i'm sure you felt that way when you had your twins-shock and fear at first, but now see how wonderfully you are parenting them and caring for them. and whether they have cf or not they are your precious babies.
as a mother, you don't know your strength till you hold your baby in your arms-then you know you will do whatever it takes to care for them. you will go to whatever lengths necessary to protect them.
come what may, you will do the same for this precious baby. whether it has cf or not, it is going to grow up with happy days and sad ones too, and you'll be there for it.