Both newborns and adults can be tested for the changed (mutated) gene that causes cystic fibrosis. These tests include:
Newborn screening. Levels of a type of digestive enzyme are measured from a blood sample. High levels of this enzyme suggest cystic fibrosis. Some newborns may also have a genetic test.
Genetic test for adults. These tests identify the most common defects in the CFTR gene. Genetic testing can be done during pregnancy through chorionic villus sampling or amniocentesis. The test can also be done before pregnancy, to help couples find out if either or both of them carry a defective CFTR gene.
If both parents carry the changed gene, there is a 25% (1-in-4) chance that their child will have no genetic problem. There is a 25% chance that their child will have cystic fibrosis. And there is a 50% (1-in-2) chance that their child will be a carrier.
If only one parent is a carrier of the changed gene, the child will not have cystic fibrosis. But there is a 50% chance that the child will be a carrier.