NPR: Blood Test Provides More Accurate Prenatal Testing For Down Syndrome

A new blood test offers pregnant women a safe and much more accurate way to screen for Down syndrome.

A study that evaluated the test in 1,914 pregnancies found that the test, which checks DNA, produces far fewer false alarms than the current screening techniques.

“It’s very good news for pregnant women,” says Diana Bianchi, a pediatric geneticist at Tufts Medical Center who led the study. “It’s very important because it means a significant proportion of women are not being made anxious by being told they have an abnormal test result.”

Bianchi and others stressed that the results of the screening test would still need to be confirmed by follow-up diagnostic tests — either amniocentesis or chorionic villus sampling, which can cause miscarriages. But the new blood test would send fewer women for that risky testing.

“That’s what we’re really concerned with at the end of the day,” Bianchi says. “That there’s an unintended miscarriage resulting from a procedure that didn’t need to be performed in the first place.”

Doctors recommend that all pregnant women get screened for Down syndrome and other trisomies, which are conditions caused by too many chromosomes. But the tests, which rely on measuring chemicals in the mother’s blood and doing an ultrasound of the back of the neck of the developing fetus, can raise flags when none are warranted in a small but significant number of cases.

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