Approximately 98% of CF men have Congenital Absence of the Vas Deferens (CAVD).
Although it use to be considered these men were INFERTILE....that is no longer considered accurate since healthy sperm is still produced.
What CAVD does is not give the sperm a way to travel from the testicals to the penis and out in the semen.
The ONLY way to know for sure if a CF man has or doesnt have this is to be tested. It should never be assumed.
For the men who have CAVD there is a procedure available called IVF where they extract the sperm from the man, take eggs from the woman, fertilize them & implant them in hopes of one succesfully taking.
Hope that answers your question~!