If you do a search, you can find a thread I started on genetic testing.
DH and I are still deciding if we want to TTC. But in mid-October we are having genetic testing done - to find out if we are CF carriers and if DH is a carrier of other things. It is important to us to know this info before we make our decision about having children. But it is definitely a decision for each couple to make on their own.
eta: Miaclear, I bumped up the other thread for you (genetic testing).