Carrier Testing for Cystic Fibrosis: Straightforward answers to important questions

CF is a condition in which mucous is abnormally thick because of an abnormality in the CFTR gene.  This results in reduced ability to fight respiratory infections and, ultimately, loss of lung capacity.  In addition, many affected individuals are unable to digest fats because of a poorly functioning pancreas.  Although longevity has increased as treatment advances have occurred, the average life expectancy for individuals with CF is 35-40 years.  Males with CF are nearly always infertile.  Affected individuals have normal intellectual abilities.  There are milder forms of CF, one of which causes absence of the vas deferens and infertility in men, but no lung disease.  Occasionally an individual with CF has very mild lung disease and few other medical problems.

CF is inherited in an autosomal recessive manner.  This means that males and females are equally likely to be affected and that both parents must be carriers of CF to have an affected child.  Approximately 1 in 25 Caucasians are CF carriers.  CF carriers have no manifestations of CF and no health problems related to being a CF carrier.  When both parents are CF carriers, there is a 25% chance in each pregnancy for the baby to be affected with CF.

• Any Caucasian woman and/or her Caucasian partner
• Women of other ethnic backgrounds
• Someone who has a relative with CF, or whose reproductive partner has a family history of CF

Genetic consultation, ideally prior to conceiving, or as early as possible after a pregnancy is recognized, can be helpful when there is a family history of CF or if other prenatal testing is being considered.

• Do you feel that CF is a serious enough condition that knowing whether a fetus is affected prior to the baby being born would be important to you?  [Newborn screening in New York and all other states includes CF testing.  With early identification, digestive problems related to CF can be effectively treated, and it is hoped that some of the lung problems may be prevented.  It is not presently possible to prevent the lung disease that eventually develops in children and young adults with CF.  However, scientists have recently made great progress, and there are several promising new drugs to treat CF, some of which are being evaluated  in clinical trials.]
• Would you handle a pregnancy differently knowing that the baby could have CF?
• Do you feel comfortable with possible uncertainty about test results?  For instance, if one member of a couple is a carrier and the other is not, there would still be a small chance of having a baby with CF.  Prenatal testing for CF would not be available in this situation.

Your obstetrician has written information on CF carrier testing.  If desired, he or she can refer you to a geneticist for comprehensive consultation.  The geneticist, after obtaining a complete family history and reviewing relevant medical information, will be able to discuss the genetic issues in more detail, arrange carrier testing if desired, interpret the results of genetic testing, and make recommendations for further testing and/or prenatal diagnosis.