+44 (0)20 7034 8945   |   78 Harley Street, London W1G 7HJ
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+44 (0)20 7034 8945   |   78, Harley Street, London W1G 7HJ
Client Support   |   Medical Terms    |   Feedback    

Non Invasive prenatal Test – NIPT

Harmony Prenatal Test

As pregnant women in all walks of life become increasingly aware of the effectiveness of NIPT, we aim to share any reduction to the cost of this service with our patients to ensure it is accessible and affordable through competitive pricing.




TDL Genetics


Option 1:
£355 ( + £50 consultation charge if scan not required)

Option 2:
£685 ( includes Harmony, 2 scans @ 10+ week and 12 week )

Option 3:
£710 ( includes Harmony, 2 scans @ 10+ week and 12 week with Nuchal blood taken)


Result available in

5-7 business days

Gestation age


Combined sensitivity for T21,T18,T13


Test success rate of eligible samples


False positive rate ( T21, T18, T13)




IVF pregnancies including egg donor


Gender information

Singleton (Yes)
Twin (No)


HarmonyTest: English, new logo on Vimeo.


The Non-Invasive Prenatal Test (NIPT) offered at the Harley Street Centre for Women is provided by TDL Genetics, The Doctors Laboratory, London, UK, and is known as the Harmony Test.

NIPT is the most accurate way of estimating the risk of a baby having Down syndrome (Trisomy 21), Edward’s syndrome (Trisomy 18) or Patau syndrome (Trisomy 13).

NIPT differs from traditional screening for chromosome abnormalities, such as, the Combined Test and the Quadruple Test because it analyses the baby’s DNA rather than ultrasound features and/or hormone levels in the blood. This means NIPT is more accurate than these traditional tests for estimating the risk of a baby being affected by Down, Edward’s or Patau syndrome.

What is Down syndrome, Edward’s syndrome and Patau syndrome?

Most of us have 23 pairs of chromosomes in each cell and each chromosome is made of a coil, which contains our genes. These give instructions to our body to tell it how to work. Down syndrome occurs when a person has an extra copy of chromosome 21. Having this extra genetic information is what causes the physical and mental characteristics of people who have Down syndrome. Edward’s syndrome occurs when a person has an extra copy of chromosome 18 and Patau syndrome occurs when a person has an extra copy of chromosome 13.

How does NIPT work?

DNA is the genetic material found in each and every cell in our body. Cell free DNA is genetic material, which originates from the baby but can be detected in the mother’s blood. The exact mechanism as to how the baby’s DNA – the cell free DNA – finds its way into the mothers blood stream is not clear. However, scientists have discovered the cell free DNA is present from early pregnancy and is undetectable 2 hours after the baby is born.

The Harmony Test works by analyzing the DNA fragments present in a sample of the mother’s blood. Each chromosome has sequences of DNA that are specific to that particular chromosome. Therefore by analyzing and counting all the DNA sequences that map to chromosomes 21, 18 and 13, it can be assessed whether there is a normal amount of sequences matching to each chromosome. If a baby has Down syndrome, there will be slightly more sequences that map to chromosome 21 than expected, indicating that there is more chromosome 21 present than normal. The same would apply for chromosomes 18 and 13. This allows very accurate prediction of pregnancies were the baby is likely to have Down, Edward’s or Patau syndrome.

What result could I get from NIPT?

There are 3 possible results from NIPT:

Positive – predicted to be affected by Down, Edward’s or Patau syndrome

Negative – highly unlikely to be affected by Down, Edward’s or Patau syndrome

Inconclusive – inconclusive results happen in less than 4% of cases. This is usually because the proportion of DNA present in the sample is not high enough to give an accurate result. NIPT may be repeated (no additional fee) with the hope that cell free DNA levels will have increased due to the increased pregnancy gestation.

How accurate is NIPT?

NIPT detects 99% of babies with Down and Edwards syndrome. For Patau’s syndrome it will detect 92-99% of babies, depending on the test you choose.

Why are the results not 100% accurate?

The only way to know for sure whether or not a baby has a chromosome abnormality is to have an invasive test such Chorionic Villus Sampling (CVS) or amniocentesis. Invasive testing gives very accurate results because genetic material obtained directly from the pregnancy is used for analysis. However, as these procedures involve inserting a needle into the womb to obtain genetic material, they carry a small but significant risk of causing a miscarriage (1%).

NIPT is a screening test and therefore in rare circumstances positive and negative results can be inaccurate. The test will detect up to 99% of babies affected by Down, Edwards or Patau syndrome. A false positive result occurs in less than 0.3% of cases (1:300). This is significantly better than traditional screening tests which have a detection rate of 75-95% for a false positive rate of 3-5%.

This means that women choosing NIPT will benefit from a test that detects a greater proportion of babies affected by chromosome abnormalities, and women will be less likely to require an invasive test (which carries a 1% chance of miscarriage) following screening.

Click here to download full patient information leaflet


The material on this site is for informational purposes only, and is not a substitute for medical advice, diagnosis or treatment provided by a qualified health care provider.

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