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.
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.
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.
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.
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.
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.
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|
|Combined sensitivity for T21,T18,T13||99%|
|Test success rate of eligible samples||>99%|
|False positive rate ( T21, T18, T13)||0.15%|
|IVF pregnancies including egg donor||YES|
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I’ve been coming here for a few years now for my obstetric care and the doctors are nothing if not excellent and highly professional. I see Pat O’Brien (obstetrician) who is fantastic and Pran Pandya (scanning and fetal medicine) , who is brilliant. Also nice that they are always on time and never make you wait.
Dr. Sadia Bhatti highly exceded our expectations and we absolutely recommend her. She is a very experienced and talented professional who displayed the highest degree of technical skill and empathy.
Meeting Dr. Bhatti reassured us that we could have a positive birth despite the challenges. She explained the options and empowered us to make the choices that felt right for our circumstances. We opted for a gentle csection, and it was the most beautiful birth.
Thank you will never be enough! We will never be able to fully express how grateful we are to you for everything you did…
Thank you again for all of your help and excellent care during my pregnancy. I am very grateful.
Thank you for safely delivering our 3 children. You made every experience so pleasant! We always felt safe in your hands!
It’s not just skill that makes a good doctor but caring as well. Thank you for the concern and expertise you displayed throughout the pregnancy and birth. I truly felt that I was in good hands. We look forward to using you again some time in the future, please G-d!
Little things make a big difference. Appointments to fit your schedule and always on time, very friendly service and meeting the same people for your appointments is very reassuring.