Quick Menu

Clinic Address

78 Harley Street

Contact Us

020 7034 8969
020 7034 8945



NIPT : Harmony Test

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.

The Harmony test 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).

The Harmony test 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 Harmony test 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 trisomy 21, 18 or 13? 

Most of us have a normal complement of chromosomes, this being 46 in total, made up of 23 pairs. In trisomy, there is an additional copy of a particular chromosome, resulting in a total of 47 chromosomes. The most frequently occurring trisomy is trisomy 21, more commonly known as Down syndrome.  Other trisomies include trisomy 18 and trisomy 13, known more commonly as Edwards and Patau Syndrome, respectively.

  • Trisomy 21 is found in around 1 in 700 births and the risk of having a baby affected by trisomy 21 increases with advancing maternal age. The condition is associated with learning disability and some structural problems within the baby’s major organs, most commonly heart abnormalities. The life expectancy is around 60 years. 
  • Trisomies 18 and 13 are found in around 1 in 7,000 births and the risk of having a baby affected by one of these trisomies also increases with advancing maternal age. These conditions are associated with severe learning disability and multiple physical abnormalities. Most affected babies die before or soon after birth, and rarely survive beyond the first year of life.  

What is the Harmony Test?

DNA is the genetic material found in each and every cell in our body. The pattern of DNA makes up the genes that code for our characteristics, such as hair and eye colour, and any genetic conditions we may have or carry. Cell free DNA is genetic material which comes from the baby but can be detected in the mother’s blood during pregnancy. The exact mechanism as to how the baby’s DNA – the cell free DNA - finds its way into the maternal bloodstream is not clear. However, scientists have discovered that cell free DNA is present from early pregnancy and is undetectable 2 hours after the baby is born. 

The HarmonyTM Prenatal Test analyses cell free DNA in maternal blood and gives a strong indication of whether the baby is at high or low risk of having trisomies 21, 18 and 13. 

How accurate is The Harmony test?

The Harmony test 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.

What would the results show?

If the Harmony test shows there is a high chance that the fetus has trisomy 21, 18 or 13 it does not mean that the fetus definitely has one of these defects. If you want to be certain you should have a CVS or amniocentesis. One of our consultants in Fetal medicine will discuss the options with you in detail.

If the Harmony test shows that there is a low chance (less than 1 in 10,000) that the fetus has trisomy 21, 18 or 13 it is unlikely that the fetus has one of those defects.

When do I expect to get the results?

The results from the test will generally be available within 1 week and we will notify you as soon as we receive them by phone or/and email.

In about 5% of cases the test does not give a result. This is due to technical problems with the analysis of the sample and does not suggest there is a problem with the baby. We will repeat the test at no cost and are able to get a result in over 50% of cases.

Result available in 5-7 business days
Gestation age 10+weeks
Combined sensitivity for T21,T18,T13 99%
Test success rate of eligible samples >99%
False positive rate ( T21, T18, T13) 0.15%
Twins YES
IVF pregnancies including egg donor YES
Gender information YES

How much does it cost?

Please note that we are led by a team of highly skilled specialist doctors that offer diagnosis and treatment of complications which may arise in unborn babies. All your scans will be performed by our experienced fetal medicine consultants. We do not offer scans performed by sonographers or fellows. The service we provide by consultants offer screening, diagnosis and management of your pregnancy to the highest standards.

Harmony + Consultation
£405 (Consultant Led)

Includes pre-test genetic counselling and Harmony test.

This option applies only if you have had a scan recently. We will ask you to bring a recent scan report (performed within 2weeks) with the measurements of the baby.

Harmony test + Scan
(Consultant Led)

Includes an ultrasound scan followed by the Harmony blood test.

Early pregnancy scan + Harmony test £545
Nuchal scan (with nuchal bloods) + Harmony test £627.50
Early Anomaly scan+ Harmony test £615
Anomaly scan+ Harmony test £640
Wellbeing scan+ Harmony test £585
Contact information
    Phone :

    020 7034 8945
    020 7034 8969

    Email :


    Address :

    78 Harley Street
    W1G 7HJ

Request An Appointment

Have more questions? See our Q&A page for more help and assistance on how we can help you to provide the clarity you need for your health.

Frequently Asked Questions

Appointments & Corresspondence

Find our clinic location below if you are booking an appointment or corresspondence - Get Directions