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£389 / £429 with ultrasound scan


Non invasive prenatal testing

The Harmony test is a blood test that looks for whether your baby has Down Syndrome, Edward or Patau Syndrome. In these conditions there are 3 copies of certain chromosomes instead of 2 (“Trisomy”). The test looks at DNA from the baby that is present in the mothers bloodstream.

This test is not currently available on the NHS. It will be available on the NHS from April 2018 for some groups of women. You can book this test at Somerset Early Scans from 10 weeks of pregnancy onwards.


This is an extremely accurate screening test and is more accurate than the combined test currently offered by the NHS.

If the NHS combined test suggests a baby is high risk for a trisomy condition, it only has a 10% chance of being correct. Having a more accurate test means less chance of having to go through the stress and unpleasantness of having an amniocentesis, a procedure with a 1 in 200 risk of miscarriage

The Harmony test is also available earlier in the pregnancy than the current standard NHS test.


Like all tests, the Harmony test has a small risk of it being incorrect. It may report a low risk of the baby being affected when in fact the baby does have the condition.

Overall the Harmony test detects >99% of babies with trisomy 21,18 &13.

For trisomy 21 the detection rate is above 99%. Trisomies 18 and 13 are rarer conditions. The reported detection rates of these is 97.4% (T18) and 93.8% (T13).

The chance of a low risk result being correct is also called the negative predictive value. This is 99.98% for all non invasive prenatal tests and 99.95% for the combined test.

There is also a false positive rate. This is when the report suggests a high probability of an affected baby when in fact the baby is not affected. For the harmony test this happens in 1 in 1000 high risk results or 0.1%. A systematic review published last year of all the evidence from various non invasive prenatal tests reported an overall false positive rate of 18%. With conventional screening methods such as those used in the NHS the false positive rate is 89%.

Very occasionally these tests can pick up a problem in the mother, not the baby.

The Harmony test can also test for the sex of the baby however a recent report from the Nuffield Council of Bioethics has advised against its use for this without a medical reason.

It also has the capability to look at the number of sex chromosomes X and Y. An abnormal number of X and Y chromosomes can cause medical problems. However, limited numbers of babies with these conditions (sex chromosome aneuploidies) have been evaluated so the accuracy of testing for this is uncertain and we therefore do not recommend it.

Non invasive prenatal testing does not diagnose other genetic or structural diseases such as spina bifida. A negative result obviously does not guarantee a healthy baby.

When to test

Any time after 10 weeks of pregnancy. Before this point there is not enough DNA from the baby in the mothers bloodstream.

What will happen

We will see you to discuss the pros and cons of testing and take your consent if you decide to go ahead. We need to have accurate dating of your pregnancy so if you come before your NHS dating scan then a scan for viability & dating will be done followed by your blood test. We will ask you how you would like to be informed of your results.

The samples are sent by Royal Mail Business Post to The Doctors Laboratory in London, who process all the UK Harmony samples in house.

A result will be received within 10 days or less and you will be contacted by us within 24 hours. Our average time from appointment to result is currently 7 days.

In 3% of cases the sample cannot be processed due to it having insufficient DNA within it. In this case we will contact you to arrange repeat testing at no additional charge. This is more likely to happen if you are earlier in the pregnancy or overweight. So if your BMI is raised you may wish to come a little after 10 weeks.

Twins & IVF pregnancies

The Harmony test can be used for IVF pregnancies, including those with donor eggs.

It can be used in twin pregnancies for screening purposes but not to look at the sex chromosomes. It cannot be used in twin pregnancies where one twin has not been viable. It is also not validated for use in triplet pregnancies.

Positive tests

If you have a test result reported as high risk we recommend seeing an Obstetrician or Geneticist to discuss the pros and cons of having an invasive test such as an amniocentesis, to provide a diagnostic result. Or to discuss a plan for care during and after the pregnancy. We will seek your consent to contact your Midwife or Obstetrician on your behalf so that this can be arranged.

Due to the small chance of the harmony test result being incorrect it is not considered to be diagnostic.

Why book with us?

We believe in informed choices so we allow plenty of time for a full discussion with you at your appointment.

The clinician who saw you will personally phone you as soon as your results are available.

In the rare event of a high risk report, we will liaise with the NHS team on your behalf, to get you seen quickly.

More information

Information about the conditions
Down Syndrome www.downs-syndrome.org.uk
Edward and Patau Syndrome www.soft.org.uk
Turner Syndrome www.tss.org.uk
Klinefelter Syndrome www.nhs.uk/conditions/klinefelters-syndrome

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