How is CF Inherited?
What is the chance my patient will have a child with CF?
CF is a genetic disorder and is one of the most common inherited diseases in the U.S. CF is passed from parents to their children through their genes, or DNA. For parents to have a child with CF, both parents must be CF carriers. If only one parent is a CF carrier, the child may inherit the defective CF gene and be a CF carrier, but will not have CF or be affected by the disease.
If both parents are carriers, the possible results are shown below:
Who should consider being tested?
The American College of Obstetricians and Gynecologists (ACOG) and the American College of Medical Genetics (ACMG) recommend the following individuals have information about cystic fibrosis (CF) carrier screening made available to them:
- All individuals of reproductive age
- Couples planning pregnancies
- Couples who are already pregnant
How can my patient get tested?
Your patient’s test results confirm if he or she is a carrier of one of the most common CF mutations. The CF carrier screening test is performed on a sample of blood. The results from this screening test are typically available within a week or two.
What if my patient tests negative?
If the results from a CF carrier screening test are negative, the chance of being a carrier and having a child affected by CF are extremely low.1
What if my patient tests positive?
If the results from a CF carrier screening test are positive, your patient is a CF carrier. Since both parents must be CF carriers for their child to have CF, the other parent should also be tested.
If the other parent tests negative, the child may inherit a defective CF gene and be a carrier. However, the chance of the child having CF and being affected by the disease is extremely low. If both parents test positive, the possible results are shown below:
If your patient is already pregnant, and both parents are carriers, then you have the option to choose additional prenatal diagnostic testing to determine if the child will have CF.
The good news is that only a small percentage of couples will both be CF carriers, and in this situation there is only a 25% chance with each pregnancy that the baby will have CF. Carrier and newborn screening programs can aid in early diagnosis of CF and, when combined with current advances in medical treatment, children with CF are living longer, healthier, and happier lives.
Is testing required?
No, CF carrier screening is optional. Talk to your patient about cystic fibrosis carrier screening and make an informed decision together.
1The test results from CF carrier screening DNA tests are extremely accurate. However, because not all rare mutations are known and/or tested for, in certain rare circumstances, a mutation in the CF gene may not be detected by this test. You may still be a CF carrier although your test results are negative.