What is the difference between nuchal translucency screening and NIPT test
Pregnancy, in addition to happy anticipation, involves many choices, including the choice of examinations and prenatal tests. To make it easier for you to choose, we have compared a review of the nuchal translucency screening and the NIPT test (by GenePlanet). Those are the most commonly performed test by pregnant women.
What is a nuchal translucency screening, and how is it done?
Nuchal translucency is the thickness of a pocket of fluid under the skin at the fetus’ neck, which is measured by ultrasound. The examination is non-invasive, harmless to the fetus, and usually carried out through the abdominal wall, exceptionally vaginally.
The examination of nuchal translucency primarily assesses the likelihood of a chromosomal defect T21, T18 and T13, which can be visible as increased thickness of the fluid pocket.
The gynaecologist can also perform a thorough general examination of the embryo’s development and determine the date of birth.
Nuchal translucency screening is performed between week 11 and 14 of pregnancy, with the procedure itself usually lasting between 15 and 20 minutes.
What is a NIPT test, and how is it done?
NIPT by GenePlanet is a non-invasive prenatal screening test that detects Down syndrome, Edwards syndrome, Patau syndrome, other trisomies, chromosomal aneuploidies as well as numerous deletion and duplication syndromes that could affect fetal development.
The test requires just a small blood sample from the pregnant woman and is completely risk-free for the baby.
Get the sample to lab and the results can be available within 6–8 business days.
The test can be performed from the 10th week of pregnancy when there should be a sufficient concentration of fetal DNA in mother’s blood.
Accuracy of test results
NUCHAL TRANSLUCENCY SCREENING
The biggest drawback of a nuchal translucency screening is that it detects between 70 and 80% of fetuses with Down syndrome. This means that in 100 babies with the syndrome, the screening will not identify as many as 20 to 30 infants.
However, if you decide to perform the double hormone test value (betaHCG and PAPP in the mother's blood), the positive predictive value increases to 85–90%.
Nuchal translucency screening also results in approximately 5% false positives, which is problematic as this may unnecessarily expose the pregnant woman to the risk of invasive diagnostic tests.
NIPT by GenePlanet is much more accurate than nuchal translucency screenings. The detection rate of the three most common trisomies present at birth is higher than 99%.
A much lower percentage of false positives is also a significant advantage:
- there are only 05% false positive T21 (Down syndrome) screenings,
- there are 14% false positives when screening for the most common chromosomal trisomies.
As a result, fewer pregnant women are unnecessarily exposed to the risk of invasive methods.
What are the tests’ findings?
NUCHAL TRANSLUCENCY SCREENING
On examination, the gynecologist measures the width of the nuchal translucency area. If the area is more than 2.5 mm wide, it is considered abnormal.
Such a result indicates an increased risk of Down syndrome. The examination also reveals a potential risk of Edwards and Patau syndrome, which are much rarer and mostly cause miscarriage in early pregnancy. If the gynaecologist concludes that the risk of chromosomal abnormality in the fetus is 1:300 or more, he will suggest further examinations.
The only way to determine the presence of chromosomal abnormalities with a 100% certainty is through an invasive diagnostic test – chorionic villus biopsy or amniocentesis. Such a test presents up to 1% risk of miscarriage, so it is not an easy decision.
Fortunately, you can opt for a NIPT test before such invasive testing.
In addition to examining nuchal translucency, you can also check the length of the cervix, cranial anatomy, spine, stomach, kidney, bladder, and check for the presence of all 4 limbs. This can help the gynaecologist identify any other abnormalities in the development of the fetus.
The NIPT test primarily reveals three most common chromosomal abnormalities present at birth: Down, Edwards and Patau syndrome. It also reveals your baby's gender, if you wish.
Additional research depends on the package you choose. E.g. the most comprehensive NIPT test by Geneplanet also reveals:
- 4 aneuploidies of sex chromosomes (Turner's, Klinefelter's, triple X and XYY syndrome),
- 3 additional trisomies (trisomies of chromosomes 9, 16, and 22),
- 60 possible deletion and duplication syndromes.
If the NIPT test shows an increased risk of any abnormality, the pregnant mother is advised to have an amniocentesis, which can either confirm or rule out the suspicion with certainty.
Which test should you choose?
The nuchal translucency screening and the NIPT test are by no means mutually exclusive procedures. It is ideal to do both, especially if you are over 35 years of age. Nuchal translucency screening can detect abnormalities via ultrasound, which NIPT cannot do as they might not be genetic. However, NIPT is more sensitive or comprehensive when it comes to chromosomal abnormalities and can offer greater peace of mind.
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