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New blood test to detect chromosomal defects

The Howard Hughes Medical Institute announced today that their researchers, together with others at Stanford University have developed a new test that can accurately detect Down Syndrome (or the so-called Trisomy 21) as well as two other chromosomal aberrations that can cause serious birth defects.

Currently, two methods are mainly used in prenatal diagnostics to detect chromosomal defects in the unborn baby: amniocentesis and chorionic villus sampling (CVS). These two methods require removing amniotic fluid by inserting a needle into the mother’s uterus. Although considered more or less safe, these methods are however invasive and present a small risk of miscarriage. The advantages of this new technique are:

  1. Non-invasive
  2. Risk-free
  3. Can be conducted early in the pregnancy
  4. Will end up to be cheaper

The idea is based on the fact that small amounts of fetal DNA are found in the mother’s blood. However, it has been a problem to find these small amounts of DNA considering that they occur in mommy’s blood at about 1 baby DNA to a million of mommy DNA. However, by using a shortcut “shotgun” approach that tested for both baby and mommy DNA, the researchers were able to overcome this obstacle.

The blood test has been has successfully demonstrated in 18 pregnant women who also underwent amniocentesis or CVS. The results of the new test completely matched those of the two conventional tests and identified 12 of the 18 pregnant women carrying babies with chromosomal defects. In addition, a man was also blood-tested for reference.

This promising test, however, is not ready to be used as standard test until proven and tested in studies involving larger numbers (thousands!) of participants. This is to make sure of the accuracy of the test considering what is at stake. In another study, European researchers report that the currently used prenatal screening methods (including amniocentesis or CVS) are not 100% accurate. In addition, they can only detect half of chromosome abnormalities (only the trisomoies) that occur in fetuses. Others are not detectable by these methods.

If you are thinking of having amniocentesis or CVS, you might also consider volunteering to participate in the study to confirm this new blood test. It’s just giving a little bit of your blood.

Others may ask, why get tested at all? I’d say, let’s respect each other’s right to choose.


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