Because a pregnant woman's blood carries pieces of fetal DNA, researchers can devise tests to tell with a high degree of certainty whether the fetus carries extra chromosomes (as an extra chromosome 21 in Down syndrome, for example). They can also test for versions of genes that cause or raise the risk for a disease, potentially screening for a whole slew of genetic disorders in one fell swoop.
And as geneticists learn more about the genetics behind traits such as eye color or hair color, these noninvasive fetal tests will be to pick up on those characteristics as well.
“Prenatal genetic...