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Down Syndrome Test Poses Ethical Questions

A test that can detect Down's syndrome from the blood of pregnant women, which would be the first reliable noninvasive prenatal test for the chromosomal disorder, has raised the prospect of routine screening for the condition for every expectant mother who wants it.

The experimental procedure, developed in Hong Kong, has been shown to diagnose 90 percent of Down's syndrome cases in a small trial, while also correctly identifying 97 percent of fetuses that do not have the condition.

If its accuracy can be improved and it is validated in larger patient trials, which scientists believe should take three to five years, it would transform prenatal testing for Down's.

At present this is provided only for women at high risk of having a Down's baby because the current procedure is invasive and can cause a miscarriage. It requires amniocentesis or chorionic villus sampling (CVS), which involve inserting a needle into the womb to remove amniotic fluid surrounding the fetus, or a small piece of the placenta.