How does NIPT work?
NIPT (Non-Invasive Prenatal Testing) is a single blood test that uses a special genetic technology to screen pregnancies for the most common chromosome differences. It can also inform you of the sex of your baby, if desired. This new test can be completed as early as 10 weeks gestation, with no risk to the pregnancy. NIPT analyzes the DNA in your blood (your DNA as well as fetal DNA) to screen the pregnancy for the following chromosome differences:
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
- Sex chromosome differences such as Monosomy X, Triple X (XXX), Klinefelter syndrome (XXY), and Jacob syndrome (XYY)
What conditions can NIPT screen for?
NIPT can screen pregnancies for Trisomy 13, Trisomy 18, Trisomy 21 and sex chromosome differences. While they are each caused by a missing or extra copy of a chromosome, they have distinct features. Please contact one of our genetic counsellors if you would like to discuss these conditions further. Alternatively, Genetics Home Reference is a useful resource to learn more about these genetic conditions. For example, more information about Down syndrome can be found here.
How Accurate is NIPT vs. MSP Insured Screening Tests?
|Chromosome||NIPT Detection Rate||Insured Screening Detection Rate1||NIPT False Positive Rate||Insured Screening False Positive Rate1|
|21||>99%||87 - 100%||<0.1%||4 - 44%|
|18||>99%||70 - 92%||<0.1%||0.3 - 1%|
|13||>99%||Not screened||<0.1%||Not screened|
1Varies depending on your age and screening test received (e.g. SIPS, IPS, QUAD)
NIPT can also screen for select microdeletions (a small, missing piece of a chromosome). Microdeletions that cause genetic syndromes occur randomly and are unrelated to a woman’s age. These syndromes are rare, so you are very unlikely to receive a “high risk” result for one. If you do, it is more likely to be a false positive than a true result. Conclusive information would require invasive diagnostic testing. The select microdeletion syndromes are listed in the comparison table at the bottom of this page.
Is NIPT covered by MSP?
NIPT is not covered by MSP, except in a few rare cases: 1) if a woman has had a prior pregnancy where the baby was diagnosed with Down syndrome, Trisomy 18, or Trisomy 13, or 2) if a woman has received a “positive screen” on a different prenatal screening test (Quad, IPS, SIPS, FTS) during this pregnancy.
Who can have NIPT?
Pregnant women of any age or background can do NIPT. However, NIPT should not be done in any of the following cases:
- A pregnancy with a “vanishing twin” or fetal demise
- Women with a history of bone marrow transplant
- Women with an active malignancy
How long into a pregnancy can one have NIPT?
There is no cut-off. However, most people prefer to do it sooner rather than later, in case a high risk result is received.
When will I receive my NIPT results?
Typically 5-7 days after your blood draw. However, this can vary based on the company completing the test and unforeseen circumstances. The blood draw can be done as early as 10-11 weeks gestation. One of our genetic counsellors will call you to discuss the results as soon as they are available. We will provide you and your pregnancy care provider with a detailed copy of the report. If any concerns are identified, we will coordinate appropriate follow-up. Insured prenatal screening options in BC do not provide final results until approximately 16-21 weeks gestation.
Can I find out the sex of the baby?
Yes, that’s an option available to you with NIPT. The accuracy is >99%. However, in <3% of cases, the fetal sex result is inconclusive. Since fetal sex is not the primary purpose of NIPT, there is no refund for an “inconclusive” result.
What types of results can I get?
- Low Risk: The chance that the baby has Down syndrome, Trisomy 18, or Trisomy 13 is significantly decreased.
- High Risk: The chance of a chromosome difference is increased. A high risk result does not automatically mean that the baby is affected. Invasive diagnostic testing (amniocentesis or CVS) is required for conclusive results.
- No Result: In a small number of cases (~2%), the test does not provide a result and a re-draw can be attempted. Of those who opt for a re-draw, approximately 70% will receive a result. In the rare case a result cannot be obtained for you, a refund will be initiated and appropriate follow-up recommendations will be discussed.
What are the next steps after NIPT?
NIPT is a targeted screen. NIPT does not replace standard methods of screening including ultrasound evaluation at 18-20 weeks gestation. PCRM also offers a First Trimester Screening program that includes an ultrasound between 11 and 14 weeks gestation where full early fetal anatomy is reviewed and your risk for pre-eclampsia is assessed (see here for more information).
Have more questions?
We know that prenatal screening options today can be quite confusing and overwhelming. Our genetic counsellors are available to answer your questions and to discuss the benefits and limitations of NIPT, First Trimester Screening and insured screening options to determine the best choice for you.
Contact us today!
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