Cystic fibrosis is a metabolic disorder characterized by generalized dysfunction of the glands and overproduction of mucus with high viscosity. This leads to chronic bronchial obstruction and respiratory tract infections, as well as disorders of pancreatic excretory function. In men with cystic fibrosis, infertility is very common.

In Europe its frequency is one in 2000 births and is considered the most common congenital metabolic disorder. Genetically, it is an autosomal recessive hereditary disorder. More than 600 mutations in cystic fibrosis are known, the most common being ΔF-508.

It is understandable that testing should be done in couples with relatives who suffer from cystic fibrosis. It is also advisable to test for cystic fibrosis couples with severe male infertility. If one of the two candidate parents bears the disease, preimplantation genetic diagnosis (PGD) may be employed to diagnose the embryo(s) prior to the embryo transfer.