Fetal DNA Test Outperforms Standard Prenatal Testing for Down Syndrome

fetal DNA testA new study published in The New England Journal of Medicine in February 2014 reveals the fact that a fetal DNA test outperforms standard prenatal testing for Down syndrome and other common disorders. According to the new research, the non-invasive method is ten times better in predicting cases of Down syndrome than ultrasound screening or the standard blood test and five times better in anticipating Trisomy 18. The fetal DNA test also diminishes the number of false-positive result and excludes the necessity of confirming positive results with costly and risky methods like amniocentesis or chorionic villus sampling.

Jennifer Fontaine, 29, is one mother who supports the non-invasive method after the standard screening showed that her fetus might be confronted with a high risk of Trisomy 18. After refusing the amniocentesis, she tried the cell-free DNA test, which concluded that her daughter was healthy. Fontaine’s case adds to the study conducted by Illumina, which found out that the fetal DNA test outperforms standard prenatal testing not only for Down syndrome, but also for Trisomy 18. Doctor Diana Bianchi, Executive Director of the Mother Infant Research Institute at Tufts Medical Center’s Floating Hospital for Children stated that “nine out of ten women who are currently being referred for further testing would not need invasive tests.”

Several companies are already selling the fetal DNA tests, which can be done if the fetus is nine or ten weeks old, because according to Bianchi, approximately 10 percent of DNA in the expectant mother’s blood is fetal DNA from the placenta. The test costs from $500 to $2,000,  and is currently not covered by insurance for women whose babies do not present a high risk of chromosomal abnormalities and is not regulated by the Food and Drug Administration. According to Doctor Michael Greene, Director of Obstetrics at Massachusetts General Hospital, the fetal DNA test is still considered “laboratory developed,” which means it cannot be sold to other companies or laboratories.


For now, the fetal DNA test which has been proved to outperform standard prenatal screening or Down syndrome is primarily used for women over 35 years old or for those who have other risk factors, because they are reportedly more at risk for having babies with abnormalities.

However, the study published in The New England Journal of Medicine involved 1,914 pregnant women who were younger than 30, were pregnant with their first child and had conceived naturally. The test led Doctor Deborah A. Driscoll, Professor of Obstetrics and Gynecology at the University of Pennsylvania, to utter that the cell-free DNA test should be “offered women universally.”

The test appeared to work differently in very obese women.

False Positives

Richard Rava, Illumina’s vice-president of R&D for reproductive and genetic health stated the screening stage is sometimes marked by false positives, but the fetal DNA test performed during the study had a 0.3 percent rate of false positives for Down syndrome, while the standard prenatal testing was 12 times higher, namely 3.6 percent and the rate for Trisomy 18 was three times lower than the one with standard testing.

The study also concluded that the cell-free DNA test was correct in anticipating Down syndrome 45.5 percent of the time and Trisomy 18 almost 41 percent. Although these tests are not offered to the general population yet , the research proved that fetal DNA test outperforms standard prenatal testing for Down syndrome and Trisomy 18.

By Gabriela Motroc


Seattle Pi 

The New York Times

Science Daily


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