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What is a Non-Invasive Prenatal Test (NIPT)?

What is a Non-Invasive Prenatal Test (NIPT)?

February 22, 2021

What a NIPT test involves, and why you might choose to have one.

Non-Invasive Prenatal Test (NIPT)

What a NIPT test involves, and why you might choose to have one.

Many parents-to-be decide they would like to find out early on in their pregnancy whether their baby has a chance of having genetic conditions such as Down’s Syndrome.

Non-Invasive Prenatal Testing – called NIPT, or a NIP test – is one type of screening test carried out during pregnancy to identify if the baby is affected by certain chromosomal abnormalities. The test examines the baby’s DNA in the mother’s bloodstream by taking a sample of blood from the mother’s arm. The test is safe for both mother and baby[1].

What is NIPT looking for?

The NIP test is specifically carried out to discover if the baby has an increased chance of being affected by Down’s syndrome (known as Trisomy 21), Edwards’ syndrome (Trisomy 18) and Patau’s syndrome (Trisomy 13)[1].

“Trisomy” is a term used to describe the chromosomal abnormality where rather than two chromosomes, which are normally present, there are three.

The NIPT test will also discover the baby’s sex as well.

Why choose to have a NIPT test?

All pregnant women in England are offered a combined serum screening test between weeks 10 and 14 of pregnancy, which consists of a blood test and an ultrasound scan usually as part of your booking appointment. However, these tests are significantly less sensitive than a NIPT test.

The ultrasound can be carried out at the same time as the pregnancy dating scan. It measures fluid at the back of the baby's neck to determine the ‘nuchal translucency’, or NT[2]. Increased NT is associated with a variety of fetal abnormalities such as genetic syndromes as mentioned above, heart defects, and poor perinatal outcomes such as miscarriage and stillbirth[3].

The results of these two tests in combination with the mother’s age enables healthcare professionals to work out the chance of the baby having Down's syndrome, Edwards' syndrome or Patau's syndrome[2].

The combined serum screening test is less sensitive than the NIPT test, with an 86% detection rate for Down’s Syndrome and 80% detection for Edwards’ and Patau’s Syndromes[1]. Here at Melio, we use the Vanadis® NIPT, which is more accurate as it is nearly 100% sensitive for Down’s and Patau’s syndromes and 91.7% sensitive for Edwards’ syndrome[1]. The NIPT test can also determine the sex of your baby with 99.6% sensitivity[1], if that is something you want to find out.

Age and the risk of trisomy

Chromosomal abnormalities are generally not inherited, which means that they do not run in families, but most happen spontaneously. The main risk factor for trisomy is the age of the mother. The chances of Down’s Syndrome and other above-mentioned syndromes increases with age, especially after the age of 35.

Source: Hook EB. Rates of chromosome abnormalities at different maternal ages. Obstetrics and Gynecology. 1981 Sep; 58 (3): 282-285.

Who can have a NIPT test?

The NIPT test is available for all women from 10 weeks of pregnancy. It is suitable for singleton and twin pregnancies, including IVF pregnancies, although for twin pregnancies it can only identify the chance of a Trisomy-affected pregnancy overall (i.e. either one of the babies being affected), rather than a twin-specific chance[1].

The NIPT test cannot be performed in multiple pregnancies greater than twins, and it’s not suitable if you have a diagnosis of cancer or chromosomal abnormalities including Trisomy 13, 18 and 21. Similarly, people who have had a blood transfusion within the last three months, or a solid organ transplant, stem cell transplant or immunotherapy within the last 12 months, cannot have a NIPT test[1].

What will NIPT test results show?

There are four possible results you can expect from a NIP test:

Low chance – means it is very unlikely that your baby is affected by Down’s, Edwards’ or Patau’s Syndromes[1].

Increased chance – means there is an increased chance that your baby is affected by Down’s, Edwards’ or Patau’s Syndromes1. “Because the NIPT can only tell you the chance of Trisomy 21/18/13, rather than an absolute diagnosis of these syndromes, if the test finds an ‘increased chance’ then further diagnostic testing will be needed,” says Dr Yuan Xu M.D. Ph.D., medical expert at Melio.

It is recommended that parents-to-be have ‘increased chance’ results confirmed by an invasive diagnostic test such as chorionic villus sampling (CVS) or amniocentesis, because in a very small number of cases the DNA from the placenta may not represent the DNA of your baby[1]. However, as Dr Xu points out: “These invasive tests are associated with a small, but nonetheless present, risk of infection and miscarriage”, and so you should discuss this option carefully with your healthcare provider.

Failed test – means that the test has not produced a result, sometimes because there is not enough baby’s DNA in your blood[1].

Inconclusive result – means the result is not clear[1].

Book a NIPT test with Melio

If you are pregnant and would like a more accurate prenatal screening test than the combined serum screening test, you can book a NIPT at one of our growing number of convenient locations today.

All our testing locations are COVID-19 secure and undergo rigorous cleaning to ensure your safety.

You can order and pay for your NIPT test online, and choose an appointment at a time and place that suits you. The NIPT test can only be performed after 10 weeks of pregnancy so make sure that you do not book the test too early. The test is ideally done after 12 weeks. Before you attend your appointment you will be asked to complete an online questionnaire about your current pregnancy, the results from your dating ultrasound scan (if you have already had one), and whether you would also like to find out the sex of your baby at no extra cost.

After the test you can expect to receive the results directly to your Melio account within 5-10 days. All test results are individually checked by one of our in-house doctors and sent to you with a personal medical report which includes any further advice and signposting you may need. If your results show there is an increased chance for Trisomy 21, 18 or 13, you will also receive some information about the condition in question, and will be advised to discuss the need for further invasive testing with your midwife.

Please use the chat button to connect with one of our specially trained advisors if you have any questions or would like to know more.

References

[1] https://www.nuh.nhs.uk/about-the-nipt-test/

[2]https://www.nhs.uk/pregnancy/your-pregnancy-care/screening-for-downs-edwards-pataus-syndrome/#:~:text=Combined%20test,as%20the%20pregnancy%20dating%20scan

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4746871/

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