Prenatal DNA test raises both hopes and worries.

nancy, Barbara Farlow discovered that her daughter Annie would be born with the genetic disorder trisomy 13, a chromosomal abnormality — and a label — that would determine her future medical care. In August 2005, Annie, not yet 3 months old, suffered a respiratory attack and was admitted to hospital. She died within 24 hours. The official cause was “complications of trisomy 13,” but Farlow and her husband still don’t know the details, despite years of inquiry. They do know, however, that someone issued a do-not-resuscitate order without their consent. “I feel that the genetic testing ultimately determined her fate,” says Farlow, who lives in Mississauga, Ontario. “She was treated as a syndrome. She wasn’t treated as a child.” A new prenatal genetic diagnostic test may soon cause a substantial increase in the number of fetuses affixed with “syndrome” labels. The noninvasive test, called chromosomal microarray analysis, allows doctors to detect submicroscopic genetic abnormalities that no other test can find. Advocates of the technology say it is safer, faster and more accurate than invasive diagnostic procedures like amniocentesis. Despite the test’s benefits, however, some worry that it will result in a flood of prenatal genetic information of uncertain significance and will lead only to confusion and undue anxiety for expectant parents. Others question whether scientists should even be in the business of cleaning up the gene pool and have evoked the dreaded “E” word: eugenics. Researchers have been able to diagnose certain genetic conditions, like Down syndrome, in fetuses since the 1960s. This has traditionally been done through karyotyping, which involves extracting cells from amniotic fluid, culturing and staining them in a lab, and examining them under a microscope. In microarray testing, fetal DNA is obtained from a pregnant woman’s blood. This eliminates the need to perform amniocentesis, a test that slightly increases the risk of miscarriage. The fetal DNA is compared to control DNA stored on a “gene chip.” It detects chromosomal anomalies 100 times smaller than those revealed by traditional tests. “I think there’s going to be a major change in the way prenatal diagnosis is done,” says Dr. Arthur Beaudet, chairman of the Department of Molecular and Human Genetics at Baylor College of Medicine in Houston, Texas. “It’s cost-effective if couples are going to terminate. For children born with severe disabilities, their lifelong care is very expensive.” Baylor is one of the few institutions openly promoting microarray testing (others include Signature Genomic LabPrenatal DNA test raises both hopes and worries CMAJ News