People with CF have two copies of the defective gene, one inherited from each parent. Approximately 1 in 19 Irish people carry a defective gene. Carriers are unaffected but if two carriers have a defective gene there is a:
25% chance their child will have CF,
25% chance their child will not have CF,
50% chance their child will be a carrier.
Why should I consider genetic screening?
If a couple has a family history of CF, it’s a good idea to get genetic carrier screening before starting a family. There are several reasons for this:
CF is inherited in an 'autosomal recessive manner'. This means that CF may be inherited when both parents carry the CF gene. If both are carriers, there’s a 1 in 4 chance that their child could be born with CF.
It helps you understand your 'carrier status'. A person could carry the CF gene without having symptoms and testing shows whether you or your partner are carriers. If one partner is a carrier and the other is not, the chance of having a child with CF is low. Knowing your carrier status helps you plan ahead.
Testing supports informed choices. If both partners are carriers, you can explore options such as:
Prenatal testing (e.g., chorionic villus sampling or amniocentesis) to test the baby for CF during pregnancy.
IVF with genetic testing (called PGD) to select embryos without the CF gene.
Testing allows for early care. Early diagnosis and intervention can help manage symptoms and improve quality of life. If a child is born with CF, understanding the genetic background can also help parents and healthcare providers plan for the child's care from early on.
How do I organise carrier testing?
Carrier testing is available to adults over the age of 16 where there is a family history of CF. This entails a blood sample which is sent to the Genetics lab in Crumlin. Wait time for results is 14-16 weeks. This test can be co-ordinated through the CF Nurses or your GP.
