Prenatal Diagnosis |
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Cystic Fibrosis
 Signs and Symptoms
Diagnosis
Treatment
Diagnosis Screening
Carrier testing, which is performed by a blood test, can detect mutations in the cystic fibrosis gene. There are over 800 genetic changes or mutations that are known to cause CF. Some CF carriers have rare mutations, which will be missed by the test. Genetic testing for carrying the gene detects 85 percent to 90 percent of the gene changes known to cause CF among Caucasians. Genetic testing identifies a higher percentage - about 95 percent -- of carriers in the Ashkenazi Jewish population, but fewer carriers in other ethnic groups. Screening is also available for other ethnic groups but is able to identify fewer carriers because many mutations have not yet been identified.
A negative carrier test does not eliminate the chance you may carry the CF gene, but can lower that chance. Some people have rare CF mutations that cannot be detected by the routine testing available. There is a small chance that someone with a negative test could be a carrier and have a child with CF.
Diagnostic Test
Chorionic Villus Sampling
Chorionic villus sampling (CVS) can detect chromosomal problems such as Down syndrome as well as other genetic diseases such as cystic fibrosis, Tay-Sachs disease and sickle cell disease in at-risk fetuses. An advantage of CVS over amniocentesis is that it is done much earlier in pregnancy, at 10 to 12 weeks, rather than at 15 to 20 weeks.
The CVS procedure involves removing a tiny piece of tissue from the placenta. Under ultrasound guidance, the tissue is obtained either with a needle through the abdomen or a catheter inserted through the cervix. The tissue is then cultured and a karyotype analysis - an analysis of the chromosomal make-up of the cells -- is performed. It takes about two weeks to receive the results.
Because the test can be performed much earlier in pregnancy, results are typically available by the end of the third month. There is a small risk of miscarriage as a result of CVS -- 1 in 100 or less. Miscarriage rates for procedures performed at UCSF Medical Center are less than 1 in 200.
For more information, please see:
Reviewed by health care specialists at UCSF Medical Center.
Last updated August 19, 2009
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