An NIPT (non-invasive prenatal test) is a screening test done during early pregnancy to screen for certain chromosomal abnormalities and genetic disorders of the fetus. It’s a bonus test and seen as optional for those who want more information about the likelihood that their pregnancy is impacted by certain trisomies. But, in some areas it can be part of routine early pregnancy testing for all patients, or recommended in specific cases where there is a higher risk of having a pregnancy with a chromosomal issue.
In this post, learn more about:
- What NIPT tests for
- If you can determine fetal sex with an NIPT
- How much NIPT costs
- How accurate NIPT tests are
- If you should NIPT test after embryo grading or PGT-A
What does NIPT test for?
NIPT tests primarily for the likelihood of the following chromosomal abnormalities:
- Trisomy 21 (Down’s syndrome)
- Trisomy 18 (Edward’s syndrome)
- Trisomy 13 (Patau syndrome)
Depending on the provider and region (there are differences between NIPT tests and they can screen for different things), many NIPT tests also include sex chromosome screening while others go deeper, beyond just the chromosomes and can screen for specific genetic conditions called microdeletion syndromes.
What is sex chromosome screening?
Screening the sex chromosomes can lead to further syndrome diagnoses. For example, if the fetus is missing an X chromosome, this is Turner syndrome (affecting females) and if there is an extra X chromosome this is Klinefelter syndrome (affecting males).
What are microdeletions?
Microdeletions are abnormalities where there is a small absence (deletion) of genetic material that disrupts the normal function of genes. Some microdeletions are specifically linked to certain conditions. For example, Williams syndrome is caused by a deletion on chromosome seven and is associated with cardiovascular problems and intellectual disability. Other microdeletions are less clear and may cause more subtle effects. Microdeletions are rare (less than one in 1,000) but can have a big clinical impact if they occur, which is why it’s become more popular to screen for this early on in the pregnancy.
Can you determine sex with an NIPT test?
NIPT can detect chromosomes, including the sex chromosomes and therefore can determine fetal sex. By analysing the cell-free DNA from the baby it can determine whether the baby is XX or XY, allowing you insight into the sex. (And offering this information much earlier than the 20-week anatomy scan.)
What is the NIPT test process?
NIPT is a blood test, with the sample taken from the pregnant person as early as 10 weeks and up to 22 weeks in pregnancy (though it’s most accurate between 10 and 13 weeks). The test works by analysing the cell-free DNA of the fetus that is circulating in the maternal blood sample.
How long does an NIPT test take?
The blood collection itself doesn’t take long—about as long as any other blood draw. After the sample is collected it’s sent to a lab to be processed and analyzed and you’ll typically receive results one to two weeks after the blood draw.
How much does an NIPT test cost?
The cost varies depending on where you live and whether the test is considered necessary; it might be covered by your health insurance plan or work benefits, or not covered at all. For example, in Canada you can opt for the Panorama NIPT Test from LifeLabs which tests for Trisomy 21, 18, 13 monosomy X, sex chromosome trisomies, triploidy, molar pregnancy, fetal sex and five additional microdeletions (this is considered an extensive and full panel)—it will run you $795 CAD.
How does the NIPT test work?
The test works by counting chromosome copies. With certain chromosomal abnormalities we know the markers based on the number of chromosomes. For example, with Down syndrome, there is an extra copy of chromosome 21 (instead of the two copies that we would expect). NIPT is considered a screening test instead of a diagnostic test because it indirectly assess the chromosomal count by analysing the proportion of DNA from chromosome 21 relative to other chromosomes. If you have a positive screening test, your doctor will likely recommend a consult with a genetic counsellor and offer a diagnostic test to confirm.
How accurate is NIPT testing?
An NIPT test is a screening test (not a diagnostic test), meaning it cannot provide conclusive answers. It can, however, assess risk. If the test comes back indicating a high risk of certain genetic conditions, further diagnostic testing (and genetic counselling) will likely be recommended to confirm the findings. This is typically an amniocentesis; a more invasive test where a needle is inserted into the gestational sac to sample the amniotic fluid which contains many cells shed from the fetus.
The accuracy of NIPT depends on several factors, including which chromosome is being analyzed, the technology of the lab test, and even the gestational age of the pregnancy. That said, NIPT is highly accurate, especially for those three trisomies we mentioned—used as a screening test for Down syndrome (Trisomy 21) some tests have suggested greater than 99 percent accuracy (in both sensitivity and specificity) in detecting the condition.
When might your doctor recommend an NIPT test?
NIPT is an elective test and not everyone will want to get it done. Sometimes it’s a personal choice of not wanting the additional information, or perhaps a financial decision not to test (remember, this one you pay for out of pocket and costs vary widely based on location and lab). It may be recommended by a doctor if you’re at a higher risk of having a child with chromosomal abnormalities (including a previous pregnancy with chromosomal abnormalities or a family history of them) or if there is an ultrasound with concerning features (these could include a thickened nuchal fold and the absence of a nasal bone in early pregnancy, both known risk factors for Trisomy 21). If you’re carrying multiples, NIPT can also assess risk for each individual fetus.
Should you still get an NIPT test if you’ve done IVF with embryo grading or PGT-A testing?
Embryo grading is a visual scoring system to describe an embryo done by an embryologist. Although a higher graded embryo has a higher chance of a successful pregnancy, it’s quite subjective and has limited accuracy: a high graded embryo might be chromosomally abnormal with the inverse (a low graded embryo might be chromosomally normal) being true as well.
Performing PGT-A allows embryologists to analyze a few cells from the outside of the embryo to assess the chromosomes. In theory, a PGT-A normal biopsy test should mean that the entire embryo is chromosomally normal.
Think of PGT-A and NIPT as complements to each other; where PGT-A screens embryos for chromosomal abnormalities before implantation, NIPT examines the genetic material of a fetus. And although PGT-A can help to ensure that the likelihood of these genetic abnormalities being present in the embryo is low, it doesn’t reduce it to zero. Also, NIPT does cover other genetic conditions that wouldn’t be detected by PGT-A. Ultimately, whether you do these tests is up to you, and many who have gone through PGT-A will feel comfortable with that reduced risk and skip NIPT, while others will prefer another line of assessment during pregnancy.