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Simple Test Could Detect Down's Syndrome

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Nov. 21, 2000 -- Doctors have shown they can detect Down's syndrome at an early stage in pregnancy simply by taking a tiny sample of the mother's blood.

The test could give parents an earlier indication of whether their baby has particular chromosomal abnormalities and eventually may do away with existing methods of detecting those abnormalities in the developing baby in the womb -- some of which carry a risk of miscarriage.

It involves looking at the mother's blood to try and find genetic material from the baby that can then be studied for abnormalities using existing laboratory testing techniques.

Researchers from Hong Kong who used the testing method say they hope it will lead to safer and more reliable ways of diagnosing fetal abnormalities.

Reporting their findings in The Lancet this week, they write: "Ultimately, prenatal diagnosis by this technique could reduce our reliance on invasive methods."

The vast majority of Down's syndrome cases are due to an accident of nature, a chromosomal abnormality that can happen to anyone, while a fewer number of cases are due to a genetic problem inherited from either the mother or father.

The most common way of diagnosing it at the moment is amniocentesis -- a test that involves inserting a fine needle through the abdominal wall to the uterus to remove a small quantity of the amniotic fluid. This fluid then undergoes biochemical and chromosomal analysis to spot certain abnormalities in the fetus.

The procedure normally is carried out between the 15th and 20th week of the pregnancy. It is often distressing for the mother because chromosome tests can take several weeks to process. This means that, if the mother opts for a termination because the results show there are defects, it has to be performed when she is well into her pregnancy.

Because of the risk of miscarriage, the test normally is only offered to women aged over 35, when the risk of Down's syndrome exceeds the risk of losing the baby because of the amniocentesis, or if there is a family history of abnormalities.

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