Non-Invasive Prenatal Testing
Non-invasive Prenatal Testing (NIPT) is a screening test available from 9 or 10 weeks gestation until the end of the pregnancy. NIPT is a blood test, and therefore poses no risk to the pregnancy. This testing can tell you if you have a higher or lower chance for having a baby with trisomy 21 (Down syndrome), trisomy 18 and other chromosome differences. NIPT can more accurately tell you the chance for the pregnancy to have trisomy 21 and trisomy 18, compared to other forms of prenatal screening, such as eFTS or STS.
How to Get NIPT
Talk with your health-care provider if you would like to get NIPT, which may be OHIP-funded or private-pay depending on your situation. In Ontario, this test can be ordered by:
- doctors (such as family doctors, obstetricians)
- nurse practitioners
In Ontario, NIPT cannot currently be ordered by midwives.
Your health-care provider may offer the option of going to a genetics centre for further discussion if there are particular concerns about your pregnancy.
When to Get NIPT
You can choose to have NIPT done as your only prenatal genetic screen in pregnancy, as early as 9 or 10 weeks of pregnancy depending on the lab. A nuchal translucency (NT) ultrasound in the first trimester can still be done where available, to provide more information about the health of the baby.
You can also choose to get NIPT later in the pregnancy after results from other screening tests (such as eFTS or STS).
Who Should Not Have NIPT?
NIPT should not be done when:
- there are signs on ultrasound of a "vanishing" twin / co-twin demise. This is a pregnancy that started as twins, but one twin is lost and the other survives. NIPT cannot be done in this case because there can be genetic material (DNA) in the blood of the pregnant individual from the twin that miscarried, and this can affect the accuracy of the test.
- there are more than 2 babies (triplets, quadruplets etc).
Funding for NIPT
Depending on your situation, the cost of NIPT will be funded through Ontario Health Insurance Plan (OHIP), or you can choose to pay for this testing yourself. Review each option below to see which one applies to your situation.
| OHIP-Funded NIPT |
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If you are expecting one baby, and meet one of the listed funding criteria, you can have your NIPT covered by Ontario Health Insurance Plan (OHIP). If you do do not meet any of the listed criteria, you can choose to pay for the testing yourself. The blood work for OHIP-funded NIPT is done at either a LifeLabs or Dynacare location, depending on which test your health-care provider arranges for you. If you are expecting twins, you can have OHIP-funded NIPT, and it is usually possible through either laboratory. There are two situations when OHIP-funded NIPT should only be done through Dynacare (and not LifeLabs):
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| Private-Pay NIPT |
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If none of the specific criteria for OHIP-funded NIPT is met, you may choose to pay for private-pay NIPT. This means that you would pay for this testing yourself, or you may get it covered through your private health insurance. If you have not had any screening in your pregnancy, you can consider starting with an OHIP-funded prenatal screening test (eFTS or STS) before deciding to pay out-of-pocket for NIPT. A "screen positive" result from one of these other tests would allow for the NIPT to be funded by OHIP. Take note that if you are paying for NIPT out-of-pocket, and later in the pregnancy you meet one of the funding criteria, you will not be able to get a refund. In Ontario, private-pay NIPT is available through the Ontario-based laboratories (LifeLabs or Dynacare), as well as through other laboratories based outside of Canada (blood samples and personal health information is sent out of the country, where the testing is performed). Prenatal Screening Ontario is unable to endorse any specific private-pay test or laboratory. If you are interested in pursuing private-pay NIPT, please talk to your health-care provider about which test might be best for you. Here are some questions you or your provider can ask if you are thinking to have private-pay NIPT:
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What Chromosome Differences are Screened Through NIPT?
NIPT will screen the pregnancy for three chromosome differences that can occur at any age, but are seen more frequently with advanced maternal age:
- trisomy 21 (Down syndrome)
- trisomy 18 (Edwards syndrome)
- trisomy 13 (Patau syndrome)
Discuss with your health-care provider whether you would like to use NIPT to screen your pregnancy for the sex of the baby and/or any sex chromosome differences (missing or extra X and Y chromosomes).
Other Conditions
Some of the NIPT labs are able to use the NIPT blood work to screen pregnancies for genetic conditions other than the ones above. Specifically, you may be told you can screen for a group of conditions called microdeletion syndromes as an additional private-pay option. These conditions happen when there are missing pieces of chromosomes (ie. deletions) and vary in severity, ranging from no symptoms to serious health and developmental concerns. Each microdeletion syndrome is rare on its own, and therefore, the accuracy of NIPT for these conditions is difficult to study. The limited evidence available tells us that NIPT results may not be as accurate for these conditions.
Current guidelines do not support the use of NIPT to screen for microdeletion syndromes at this time, but this may change as more studies are done.
How Does NIPT Work?
During a pregnancy, there are small pieces of genetic material (known as DNA) from the placenta that can be found in the bloodstream. The placenta and the baby usually have the same genetic make up.
NIPT looks at this placental DNA and can tell if there is a high or a low chance for each of the chromosome differences that are screened. It is important to remember that NIPT is a screening test and will not give a definite answer about any of the chromosome differences.
Illustration adapted from Genetic Counseling Aids, 7th Edition, Copyright 2020, permission for use granted by Greenwood Genetic Center
How Well Does NIPT Work?
Most pregnancies that do have trisomy 21, trisomy 18 or trisomy 13 will be flagged as "high risk" through NIPT. Rarely, NIPT will flag a pregnancy as "high risk" even though one of these chromosome differences is not present.
| Chromosome difference | Detection rate | False positive rate |
|---|---|---|
| Trisomy 21 | more than 99% |
0.1% |
| Trisomy 18 | 96% | less than 0.1% |
| Trisomy 13 | 92% | less than 0.1% |
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Notes |
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The detection rate and false positive rate for the screening tests were obtained from Ontario data (twin pregnancies were not included) with an estimated date of delivery between 01-Sep-2016 and 31-Mar-2021. Detection rate = the proportion of pregnancies that are flagged as "high risk" by this test and the baby really does have the chromosome difference. False positive rate = the proportion of pregnancies that this test will flag as "high risk" but the baby does not really have the chromosome difference. |
How Long Does It Take to Get Results?
It takes approximately 7 to 10 business days for your health-care provider to receive the results of your NIPT. If NIPT was done through LifeLabs or Dynacare, you will not be able to review the results directly online.
What Will the NIPT Results Mean?
Once you get your NIPT results, you may wish to know how accurate the results are, and next steps.
You will most likely receive a “low risk” result, which means it is very unlikely that the pregnancy has one of the screened chromosome differences.
Some individuals will receive a “high risk” result, which means there is a significant chance that the pregnancy has one of the screened chromosome differences, but it is not for sure. More testing will be offered to you.
Benefits
There are three main benefits of NIPT:
| More accurate than other screening tests |
| NIPT is a more accurate screening test compare to other available tests (eFTS or STS) |
| Earlier timing than other screening tests |
| NIPT can be done earlier than other available screening tests (as early as 9 or 10 weeks of pregnancy). |
| No risk to pregnancy |
| As other screening tests, NIPT poses no risk to pregnancy. |
Limitations
NIPT has some of the following limitations:
| Not diagnostic |
| NIPT is a very good screening test but it still cannot give a definite “yes” or “no” answer. Only diagnostic testing (e.g. chorionic villus sampling or amniocentesis) can do that. |
| Does not screen for "everything" |
| A "low risk" result does not guarantee the birth of a baby without any health concerns. |
| Possibility of failed results |
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Occasionally, the NIPT can “fail” to give a result. You may not get a result for any of the tested chromosome differences. Alternatively, you may get a result for trisomy 21, trisomy 18 and trisomy 13 but the screening for sex chromosome differences may fail. NIPT can fail for many reasons. Further testing will be offered to you. On the other hand, other forms of available screening (eFTS and STS), will only vary rarely fail to give you a result. |
| Possibility of unexpected results |
| Even more rarely, you can get a result that is not typical or expected. For example, NIPT may pick up a genetic difference in your own DNA. This type of result should be further reviewed with a genetic counsellor who can discuss options for further testing. |
NIPT after Preimplantation Genetic Testing for Aneuploidy (PGT-A)
Some pregnancies happen after in vitro fertilization (IVF), and the embryos may get Preimplantation Genetic Testing for Aneuploidy (PGT-A) during that process. PGT-A involves screening embryos for chromosome differences, including trisomy 21 and trisomy 18. It is a very good screen, although it is not diagnostic. If your pregnancy was screened using PGT-A, you can consider seeing a genetic counsellor to discuss the benefits and limitations of having NIPT in your situation.
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