Prenatal screening halves CF births: data from large screening program.(News)

LOS ANGELES -- The nation's largest prenatal cystic fibrosis screening program identified 2,003 carriers of CF gene mutations in its first 4 years and resulted in the births of half the expected number of babies with the disease.

The program is operated by Kaiser Permanente of Northern California, a 3-million member health maintenance organization. Its guidelines call for screening the DNA of any willing pregnant woman who describes herself or her partner as having white ancestry, using a panel of 37 common or relatively common cystic fibrosis mutations. Patients with positive results are offered genetic counseling and CF screening of their partners. Prenatal diagnosis is then made available to couples found to be at high risk of carrying a fetus with CF, Dr. David R. Witt said at the annual meeting of the American Society of Human Genetics.

In all, 56,000 prospective parents have been screened and 2,003 carriers found, for a carrier identification rate of 1 in 28, said Dr. Witt, who is a medical geneticist and the director of the CF prenatal screening program based in San Jose, Calif.

The program has followed 71 pregnancies in 57 identified high-risk couples in which both partners were found to be CF carriers. The most commonly identified mutation combination was [DELTA]F508 in both parents.

A few of those pregnancies ended in natural miscariages. In others, prenatal diagnosis determined that the fetus was merely a carrier of the mutation or had no mutation.

But in nine cases, prenatal testing predicted severe CF, and the parents opted in all cases to terminate the pregnancies.

Two more pregnancies were terminated when parents learned that the fetus was a compound heterozygote for one severe and one mild mutation and was predicted to have mild CF or to be unaffected, he said.