Cystic fibrosis, along with its other effects, often causes fertility issues in men and women. While for women the reduced fertility is a side effect of the symptoms of the disease, in men it has a much more direct and much stronger link. Most of the time, the vas deferens is completely absent.
However, men who have cystic fibrosis yet desire to have children still have avenues open to them. There are various methods of harvesting sperm to use via in vitro fertilization to induce a pregnancy with their partner. Caution must be taken, however, to assess the risk of causing cystic fibrosis in any resulting children.