DNA Test may Help Determine Fetal Disorders in Pregnant Women

Genetic testing can be complicated and nerve wracking, but nevertheless, an important part of preparing for any future illnesses that a new baby might have.

Yet a new blood test may be able to screen for certain genetic disorders in unborn children. According to a recent study, researchers set out to examine the effectiveness of different screening tests by reporting on one particular DNA test.

Lead study author executive director of the Mother Infant Research Institute at Tufts Medical Center in Boston, MA, Dr. Diana Bianchi, compared the effectiveness of different genetic testing methods to the Illumina Inc's genetic test. They found the Illumina Inc's genetic test to be more reliable in most cases of trisomy disorders when comparing it to ultrasound tests and blood draws. Illumina's test, Verifi, also contained a lower rate of producing false positives.

The test works by counting the number of DNA fragments that are closely linked together with trisomy disorders, including Down syndrome. Then the test picks up a higher number than usual of DNA fragments, this could signify that the unborn fetus has some kind of disorder. If so, the expectant mother may need to undergo a conclusive diagnostic test for more information, including amniocentesis or chronic virus sampling.

"The current testing scares the wits out of a very large number of women, relatively speaking, who when they go through further testing are found to have totally normal fetuses," said Dr. Michael Greene, chief of obstetrics at Massachusetts General Hospital, via the Los Angeles Times. Greene was not involved in the study. "With this new test, the number of women who get inappropriately or improperly labeled as having an abnormal fetus is very small. So that's a major advantage."

The American Congress of Obstetricians and Gynecologists as well as other expectant mothers over the age of 35 have approved use of the genetic tests, as this group are at a higher risk for fetal disorders.

For their study, researchers recruited 1,914 low-risk women from U.S. cities who were pregnant with one child. They then administered a DNA test and standard tests for all women. The team calculated that the false positive rate for various DNA tests for Down syndrome was 0.3 percent. The false positive rate for the standard tests was 3.6 percent. Out of 1,365 female patients who were tested during their first or second trimester, 51 showed false positives from the standard tests whereas only four had false positives from the Illumina test. Similar results were reported for the remaining 544 women tested during the third trimester.

More information regarding the study can be found via the New England Journal of Medicine.