New test for Down syndrome

New test for Down syndrome

A more accurate test that enables pregnant women to test their foetuses for Down syndrome without the risk of miscarriage is now available in South Africa.

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The Harmony Prenatal Test makes it possible to analyse a baby’s DNA for Down syndrome by taking a sample of the mother’s blood, without any risk to mother or baby.

Doctors Shannon Morris and Karin Norman, directors of The Fetal Assessment Centre in Cape Town, decided to bring the test to South Africa after seeing clinical evidence of how it worked from the  Harris Birthright Research Centre for Fetal Medicine in London.

The traditional screening test for Down syndrome involves an ultrasound and blood test, both of which look for abnormalities in the baby.

However in 5% of women, these tests will have a false-positive result. This means that the test will indicate for Down syndrome when in fact the baby is perfectly healthy.

These mothers may choose to have more invasive tests done to determine whether their baby has the chromosome disorder, but these carry a risk.

“The existing diagnostic tests on offer – chorionic villus sampling, which involves testing a small sample of the placenta, or an amniocentesis which tests the amniotic fluid around the baby – both carry a risk of causing a miscarriage,” said Dr Morris.

One in 100 women risk losing their unborn babies due to these invasive tests.

“This means that some mothers are going to risk an unnecessary invasive procedure and risk losing their baby so that they can be 100% sure. Whereas with the Harmony test we would have to screen 1000 mothers for one to screen false-positive,” explains Dr Morris.

The Harmony test is particularly good news for older mothers, as the chance of having a baby with Down syndrome increases with age. For example, if a mother is 20-years-old, the chance of her baby being born with the chromosome disorder is one in 1000. However, if a mother is 40-years old that risk increases to one in 90.

“With the Harmony test we are virtually 100% sure of whether your baby has Down syndrome,” says Dr Morris. “And we achieve this without any risk to mother or baby and without ever having to stick the needle in.”

The Harmony Test is performed when a woman is around  ten weeks pregnant.

As a baby develops, a small amount of their genetic information (cell-free DNA) passes into the mother’s blood. This cell-free DNA can be tested to give the most accurate estimation of the risk of a baby having Down syndrome.

After the blood sample is taken at The Fetal Assessment Centre it is sent overseas to Ariosa Diagnostic laboratory in California, United States for analysis

“Ariosa has years of experience in cell-free DNA analysis which is why we opted to use their laboratory services,” says Dr Karin Norman.

And despite the distance travelled, the turnaround time for results is roughly 12 days.

“This means that we have the results before mothers come in for their 12 week scan, giving them increased peace of mind by providing early opportunities for making vital decisions during their pregnancies,” explains Dr Morris.

The biggest problem with the Harmony Test is that it costs some R8000.

This high price tag makes this test inaccessible to the state and therefore also to any mother who relies on state-provided health care. And with medical aids being unwilling to foot the bill, only those who can afford to pay out of pocket will be able to access the Harmony test.

The test is also only available in Cape Town.

“There are other centres in South Africa that know about the test but they haven’t managed to set it up yet because of the high expense involved,” says Dr Morris. “But hopefully as the technology becomes cheaper and the demand for the test grows it will become more accessible to mothers around the country.” – Health-e News Service.