New Down Syndrome Test Could Cut Healthy Baby Deaths

First large study says test could cut 98 percent of invasive prenatal tests.

ByABC News
January 11, 2011, 6:04 PM

Jan. 12, 2011— -- Lynn Harris, pregnant for the first time and in her late 30s, faced a decision many older women at higher risk for Down syndrome babies are asked to make: choose a form of prenatal testing.

"Such a brutally tough call," wrote Harris, a New York City journalist, in an article on the topic on Babble.

"I talked to friends, I spread-sheeted statistics, I lay awake."

Instead of amniocentesis, which would require her to wait until 18 to 20 weeks, she chose chorionic villus sampling (CVS) -- an invasive test which, like amniocentesis, carries a risk of miscarriage.

Right after the procedure, Harris lost most of her amniotic fluid and lost an otherwise healthy baby at 12 weeks. "I am still not over it," she said.

Pre-natal screening for Down syndrome, which affects 1 pregnancy in 691, is fraught with unclear test results, risks to the unborn baby and profound anxiety for expectant mothers and their partners.

But now, a new maternal blood test has the potential to reduce the number of women referred for invasive testing for Down syndrome by 98 percent.

A study, led by researchers at Li Ka Shing Institute of Health Sciences at The Chinese University of Hong Kong (CHUHK) and published this week in the Journal of British Medicine (BMJ) looked at the new technology, which uses the latest tools in gene sequencing to detect abnormalities in the fetus.

This technology was developed in 2008, but this is the first large-scale study, including more than 750 blood samples from pregnant women in Hong Kong, Britain and the Netherlands -- 86 from those who were carrying a child with Down syndrome.

The most robust version of the new blood test tested on 314 pregnancies detected Down syndrome in 100 percent of the cases, with only a 2.1 percent false positive rate.

"Over the years, several versions of the test have been developed, but this test is one of the most promising in terms of diagnostic performance," said Dr. Rossa Chiu, first author of the study and a clinical chemist at CUHK.

"The availability of the safe DNA blood test could therefore greatly reduce the number of pregnant couples having to bear the emotional burden of going through a potentially risky and daunting procedure, like amniocentesis."

The study is being hailed as a breakthrough.

"This paper is a proof of concept that fine-tunes the nitty-gritty science behind these upcoming prenatal noninvasive diagnostic testing," said Dr. Brian Skotko, a clinical fellow in genetics at Children's Hospital Boston and an expert in Down syndrome.

"In short, the science is getting even better, but the controversies and the overall conceptual frameworks are the same: One day soon, expectant mothers will have the option of knowing in the first trimester whether or not they have a fetus with Down syndrome without any risk to the pregnancy."