Obstetrics - OB Tests and Procedures - Cystic Fibrosis

Cystic Fibrosis Screening

Cystic fibrosis (CF) is a genetic disease that occurs more frequently in the Caucasian population.  About 1 in 3000 children are born with CF. Classic CF causes disease of the lungs and pancreas.  This may result in frequent illnesses, hospitalizations, and even death.  However, the disease course is variable.  Some individuals have very few medical problems, and with modern treatments survive well into adulthood.  Currently the average age of survival is 30.

Because of recent advances in genetic technology, we can now determine who is a carrier of CF by testing a blood sample for mutations that cause CF. Approximately 1 in 29 Caucasian individuals is a carrier, and carriers are at risk for having children with the disease. However, before considering CF screening, you should be aware of these facts.

Both parents must be carriers before a child can have the disease.  If one partner is found to be a carrier, the other would need to be tested.
If both parents are found to be carriers, the fetus has a 1 in 4 chance (or a 25% risk) of having CF. The next step would be to consider testing the pregnancy by way of amniocentesis or CVS.  There is no cure for CF; the couple could consider the option of termination if CF is diagnosed.

Although there are more than 900 mutations that cause CF, most labs only test for 30.  The CF screen detects only about 85% of mutations that cause CF. Therefore; a ‘negative screen’ does not guarantee that the individual is not a carrier.

If one person is found to be a carrier and the other is screen-negative, no further testing is recommended.  No further testing will either rule out or diagnose CF.

It is not possible to predict the severity of CF disease in a fetus that is found to carry the mutations that cause CF.


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