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New ‘More Sensitive’ Test for Down’s Syndrome in Pregnancy

Author: Neil Fearn  Bullet  Dated: 17/06/2013

Researchers at King’s College London have developed a new and more accurate test for Down’s syndrome in unborn babies. The test will use foetal DNA in the pregnant mother’s blood and will be a more definitive way of detecting whether the unborn baby has Down’s syndrome.

The test is currently being piloted in Chatham, Kent and is said to reduce the need for women to have more extensive testing which has a 1 in 100 chance of causing a miscarriage.

New test for Down’s in pregnancy

The new test involves taking a sample of the pregnant mother’s blood and testing foetal DNA. A study of 1,000 pregnancies found that the test can determine a 99% chance that the baby will have Down’s or a 99% chance that the baby will not.

This is a significant improvement on current tests which can only give a calculation of a 1 in 150-700 chance.

The new test is also less likely to lead to a false result as it is much more sensitive and accurate.

Professor Kypros Nicolaides, who is leading the research said: "This test is nearly diagnostic. It tells you almost certainly if your baby has Down’s or almost certainly if it does not. From a woman’s perspective, that is a much more clear message about what to do next."

"If the risk is say one in 250, how do they decide? When they have much more clarity, a clearer result, it is made easier."

Reduces the need for more invasive tests in pregnancy

All pregnant women are screened at their 12 week ultrasound to determine the risk of their baby developing Down’s or other genetic disorders. Of approximately 600,000 foetuses tested per year, 30,000 of those are deemed at high risk of developing Downs as a newborn baby.

However, as current testing is not accurate, these women are offered a more invasive second testing such as Chorionic Villus Sampling (CVS) of the baby’s placenta or testing of the amniotic fluid. Both of these tests carry a 1 in 100 chance of miscarriage, causing approximately 300 miscarriages a year.

Because the new test for Down’s in pregnancy is more accurate, it is said to reduce the need for women to have this more invasive testing. Also, a failure to diagnose Down's syndrome antenatally could result in a wrongful birth case.

Scientists at King’s College London claim the new test will reduce the number of women being referred for these more invasive tests from between 3-5% of pregnant women to 0.5%. The test will also reduce the number of miscarriages.

Unfortunately, due to the cost of the new test being around £400 as opposed to £150 for current Down’s testing, charities warn that these new tests will not be introduced any time soon. It could be many years before it becomes available as no laboratory in the UK is equipped to carry out the analysis.

However, researchers are hopeful that if the pilot study is successful, then pharmaceutical bosses will decrease the price of the procedure.

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