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 abnormalities. It can also inform you of the gender 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 abnormalities:
- 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 (https://ghr.nlm.nih.gov/ ). For example, more information about Down syndrome can be found here.
How Accurate is NIPT vs. MSP Insured Screening Tests?
|Chromosome||NIPT Detection Rate1||Insured Screening Detection Rate2||NIPT False Positive Rate1||Insured Screening False Positive Rate2|
|21||>99%||73 – 100%||<0.1%||3 – 27%|
|18||97.4%||80 – 90%||<0.1%||0.4 – 1.7%|
|13||93.8%||Not screened||<0.1%||Not screened|
1Norton et al. Am J Obstet Gynecol. 2012 Aug;207(2):137.e1-8; Nicolaides et al. Am J Obstet Gynecol. 2012 Nov;207(5):374.e1-6; Ashoor et al. Ultrasound Obstet Gynecol. 2013 Jan;41(1):21-5; Verweij et al. Prenat Diagn. 2013 Oct;33(10):996-1001; Ashoor et al. Am J Obstet Gynecol. 2012 Apr;206(4):322.e1-5; Sparks et al. Am J Obstet Gynecol. 2012 Apr;206(4):319.e1-9; Gil et al. Fetal Diagn Ther. 2014;35:204-11; Norton M, et al, N Engl J Med. 2015 Apr 23;372(17):1589-97; Harmony data on file; Juneau et al. Fetal Diagn Ther. 2014;36(4):282-6.
2Varies depending on your age and screening test received (e.g. SIPS, IPS, QUAD)
When will I receive my NIPT results?
NIPT results typically only take 5-7 days from the day of the blood draw and therefore, can be available as soon 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.
What types of results can I get?
- A low probability result means that the chance of Down syndrome, Trisomy 18 or Trisomy 13 is low (less than 1/10,000 chance). Almost all pregnancies that are unaffected by these chromosome problems will receive a low probability result.
- A high risk result means that the chance of a chromosome problem is increased. Greater than 99% of pregnancies with Down syndrome, 97% of pregnancies with Trisomy 18 and 94% of pregnancies with Trisomy 13 will be flagged as high risk. A high risk result does not mean that a pregnancy is actually affected. Only definitive testing with CVS or amniocentesis can determine the true presence of a chromosome problem.
- A no result/re-draw request is uncommon but possible. The rate of no result/re-draw requests is about 2%. 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 very targeted screen. NIPT does not replace standard methods of screening including ultrasound evaluation at 18-20 weeks. 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 (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!
Phone: 604-422-7276 or Toll Free: 1-866-481-7276