Finally there is an alternative to poking a needle into a mother's womb to test her baby for genetic abnormalities. Last week (October 17), researchers at Sequenom, a genetic diagnostics manufacturer based in San Diego, California, announced the release of MaterniT21, which uses a sample of the mother's blood to test for Down syndrome in the fetus. Specifically, it measures the abundance of DNA that comes from chromosome 21—normally around 1.35 percent of the DNA in the blood. An overabundance of chromosome 21 sequences suggests the fetus may have Down's, which results from carrying an extra copy of the chromosome.
The test boasts a false positive rate of just 0.2 percent, and is being marketed as an additional test to follow up on ultrasound predictions of Down's, which carry a 5 percent false positive rate.
According to Nature, MaterniT21 is the first of many, as prenatal genetic screening enters "a long-anticipated era" of non-invasive testing. "There's every reason to think that in the future you'll be able to extract an enormous amount of information from [the fetal DNA carried in the mother's blood]," Peter Benn, director of the Diagnostic Human Genetics Laboratories at the University of Connecticut Health Center in Farmington, told Nature.
While such tests could decrease the number of women who have amniocentesis—a procedure involving the extraction of a small amount of fluid from the amniotic sac, which risks injuring the baby's limbs and even miscarriage—bioethicists worry that the availability of non-invasive procedures could raise other issues, such as the decision of whether or not to keep an unhealthy fetus or the possibility that parents will make such choices on less serious conditions.