Family Matters

Can a New Blood Test Make Babies with Down Syndrome Disappear?

  • Share
  • Read Later

What if new tests for Down syndrome could one day mean no more affected babies are born? Is that cause to celebrate medical advances or reason to worry we are callously weeding out the less-than-perfect in our midst?

The possibility is on the horizon now that researchers in Hong Kong have announced they’ve developed a test that relies on DNA technology to scan the mother’s blood for indications of Down syndrome. The new screen could help most moms-to-be — 98%, according to the authors — avoid more invasive forms of testing.

“This test brings a lot of anticipation and welcome benefit, but it ushers in a whole host of provocative questions,” says Brian Skotko, a doctor in the Down syndrome program at Children’s Hospital Boston who also chairs the clinical advisory board for the National Down Syndrome Society. (More on 5 Things for the New Mom Who Has Everything)

Also called trisomy 21, Down syndrome means a fetus carries an extraneous copy of the 21st chromosome; the physical and mental impairments that result occur in about 1 of every 800 births. Women over 35 — classified as “AMA,” or “advanced medical age” — are at greater risk.

In 2009, Skotko published an article in Archives of Disease in Childhood that showed a 15% decrease in births of babies with Down syndrome between 1989 and 2005 in the U.S., which he attributed to more sophisticated prenatal screening. Without that screening, it would have been realistic to expect a 34% increase in births, since woman are having babies later.

There are various ways to detect Down syndrome pregnancies. In the past decade, nuchal translucency screenings, which use ultrasound to measure the amount of fluid at the back of a fetus’ neck, have teamed with blood tests that measure proteins to offer odds that a woman is carrying an affected fetus. (More on 5 Pregnancy Taboos Explained (or Debunked))

For those seeking certainty, invasive tests such as amniocentesis or chorionic villus sampling (CVS) are available. Though largely safe, particularly when performed by experienced practitioners, there are risks of miscarriage — between half a percent and 1% is the general estimate for amnio.

To figure out whether the DNA blood test works, the researchers — led by Dennis Lo at The Chinese University of Hong Kong — used DNA technology to analyze blood from 753 pregnant women in Hong Kong, Great Britain and the Netherlands who were considered at high risk of having a baby with Down syndrome. Testing revealed that 86 women were carrying an affected fetus. Other blood tests available to detect the condition carry the risk of false positive results, which results in anxiety and unnecessary further testing, but the DNA-based blood test is highly accurate, according to results of the research, which was published this week on the website of the British Medical Journal.

The test is still under development — it’s too expensive, for one thing — which gives medical professionals and pregnant women time to consider the implications of being able to discern Down syndrome with a simple blood test. (More on Time.comWhy It’s Harder For Older Women to Have Healthy Babies)

Various studies have shown that when women receive a definitive diagnosis, up to 90% choose to terminate their pregnancy. But most women do not elect to have an amnio or CVS; in many cases, especially for younger women, the tests are not indicated. Once the new DNA blood test is ready for the mass market, however, it will likely be offered to all pregnant women as a cost-effective method of detecting Down syndrome.

Skotko worries that doctors won’t be able to adequately counsel a pregnant woman about the reality of having a baby with Down syndrome. In 2004, a Special Olympics study found that 81% of medical students reported they get no medical education about people with intellectual disabilities.

“If that’s the case and we have a new prenatal test coming around the corner,” he says, “we’ll have a greater number of women being faced with a decision about which they don’t have accurate and unbiased information.

“Will babies with Down syndrome slowly disappear, then babies with trisomy 18 and trisomy 13?” asks Skotko. “As a clinician, I raise it as an open question. It’s a question of which forms of life are valuable.”

Related Links:

Customized Kids: Parents Abort Twin Boys in Quest for Daughter

Down Syndrome Goes Viral, Thanks to a High School Touchdown