Mums-to-be can now have their unborn babies screened for Down’s Syndrome earlier than ever before thanks to a new test.
The Harmony Non-Invasive Prenatal Test – which is offered to patients privately here in the North East – also screens for genetic conditions to give parents-to-be the extra reassurance of a normal pregnancy weeks before NHS tests are carried out.
Sadly the new screening is not yet available on the NHS, meaning anyone who wants that extra peace of mind needs to fork out a whopping £450. Although if you’re an older mum who is anxious about your baby having a chromosomal abnormality such as Downs, Edwards or Patau’s syndrome, it is certainly worth thinking about.
While I fell into the high-risk category because of my age, I wasn’t informed of this test until after I’d passed 20 weeks’ pregnant by which point it was too late. I would have most definitely taken it for the additional peace of mind if it had been available to me.The non-invasive procedure, which is carried out around the 12-week stage, involves taking a blood sample from a vein in mum’s arm, which means there is no risk to the unborn baby, while the test’s accuracy can identify 99.9% of fetuses affected by Down’s Syndrome, compared with other screening tests which identify 84%.
What is the Harmony test?
It has been found that by taking a blood sample from a mum-to-be during early pregnancy can be analysed for cell free fetal DNA, which is essentially a marker in the mother’s blood of the DNA of the baby. The result of the simple blood test (Harmony), taken at around 10-12 weeks or later has a detection rate of more than 99% in Down’s syndrome, 97.4% of Edwards syndrome and 93.8% of Patau’s syndrome, with a false positive rate of less than 0.1% which will hugely reduce the need for invasive testing by CVS or amniocentesis. It is important that an ultrasound scan is performed just before the blood test to confirm the pregnancy, and to check that the mother is not carrying twins or more. The Harmony test can be used to check twins with a detection rate of 90% and can now be used if the pregnancy is conceived with donated egg.
Why have it done?
The test is now one of the most accurate non-invasive tests to detect the chance of a chromosomal abnormality in a pregnancy (Positive predictive value ‘PPV’ greater than 99% for Down’s Syndrome). Until now doctors have been using the results of the Nuchal Translucency Scan to advise pregnant women and their partners on their risk of having a baby with Down’s syndrome, or other abnormalities. The Nuchal Translucency Scan looks at the skin fold on the back of the baby’s neck at about 12 weeks. This has been further refined by looking at the nose bone of the baby with an additional blood test to identify two pregnancy hormones. This called the combined test and has achieved a predictive value of about 84%. Women with a high risk have an option to proceed to CVS or amniocentesis. These are invasive tests that carry a miscarriage risk of about 1:100.
How it works:
A small amount of DNA from the unborn baby always circulates in mum’s blood stream. This new technology allows a small amount to be identified. Any results which indicate a high risk would then require a further diagnostic test. Expectant mothers are still advised to have their usual ultrasound scans and testing for Down’s Syndrome as part of their routine NHS care.
What is involved:
Before a sample is taken, the mum-to-be will have a preliminary ultrasound scan to ensure the gestational age and wellbeing of the pregnancy. Blood is then taken which is sent to a company in the USA to carry out the test on the DNA extracted from the blood sample.
When will I know the results?
The result is available within three to 10 days, the normal turnaround time is five days. The result is expressed as a probability. It is a screening test and not a diagnostic test. A low risk test result gives a risk of a chromosomal problem of less than 1:10000. A high risk result gives a risk of greater than 99%. A high risk result does not confirm that the baby has the chromosome abnormality. An amniocentesis or chorionic villous sampling would then be necessary to give a diagnosis.
Are there any problems the test will not pick up?
Yes. Structural abnormalities such as Spina Bifida, heart defects and a poorly growing baby will only be seen on scans and often not until later scans. These scans should still be undertaken.
Anyone wanting to find out more can contact the RVI’s Fetal Medicine Unit on 0191 282 5837 or alternatively to find other areas where the tests are being carried out, visit the developer’s website here.