Improving Prenatal Testing

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"In general, it's a great study," said Dr. David Chitayat, head of the Prenatal Diagnostic and Medical Genetics Program at Mount Sinai Hospital in Toronto, Canada. "But we need to expand it."

Most of the patients involved in the study sought out the testing because of advanced maternal age. Chitayat says he would like to see results for a wider array of patients. Chitayat was not involved in the Baylor study, but he's working on another research project involving aCGH for prenatal diagnosis, and he hopes to publish the results soon.

As with any prenatal diagnostic testing, aCGH brings with it a host of questions about how much information is too much.

"The downside of aCGH is you pick up these copy-number variants that may or may not have clinical significance, and in the worst case [the impact] may be unknown," says Diana Bianchi, professor of pediatrics, obstetrics, and gynecology at Tufts University School of Medicine and the editor in chief of Prenatal Diagnostics. Knowing that an unborn child has genetic abnormalities but not knowing how those might affect the child's development could leave many parents scared and confused, Bianchi says.

Price is another factor that could impede the use of aCGH. Beaudet says that an array currently costs $1,600. That's far more than a karyotype, which costs between $500 and $700. (The tests reported in the study were performed on a fee-for-service basis.) But Beaudet believes the price of an array could drop significantly if the volume of tests performed increases.

Currently, karyotyping and aCGH also require invasive procedures--either extracting amniotic fluid or going into placental tissue--to retrieve samples for testing, and miscarriage can result. "The next big breakthrough would be to be able to [test] a maternal blood sample or a maternal Pap smear," says Beaudet, so that the baby wouldn't be put at risk. Several research teams are currently working on techniques for isolating fetal cells that float around in a pregnant woman's bloodstream.