NIPT is a maternal blood test that screens a pregnancy to see if the baby has an increased risk of common chromosome abnormalities such as Down syndrome. The test can be done as early as 10 ½ weeks gestation.
By taking a blood sample from the mother, genetic material (DNA) from the pregnancy is measured to look for too few or too many copies of chromosomes (packages of DNA) in the baby. When the baby has three copies of a chromosome instead of the usual two, this is called a trisomy.
What does NIPT test for?
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13
- Sex Chromosome abnormalities
NIPT is the most accurate blood test for common fetal trisomies. It has a detection rate of up to 99% and a low false positive rate of <0.2% (a” false positive” is the chance of having a “high risk” result if the baby does not have Down syndrome)
NIPT, like other prenatal screening tests, is not considered diagnostic (100% accurate). If the NIPT result is abnormal, you will receive counselling from Dr. Wise or a genetic counsellor and be offered diagnostic testing, like amniocentesis, which will give definitive results.
Who Is Eligible for NIPT?
This test is not yet widely available in B.C. although any patient can choose to pay for it privately. You may qualify for a funded NIPT if:
- You have a Positive Screen result from IPS, SIPS, or Quad.
- You had a previous trisomy 13, 18, or 21 pregnancy.
- Your risk of Down syndrome is greater than 1 in 300 based on results of screening and ultrasound marker(s) of aneuploidy.
What are the next steps after NIPT?
We recommend that you continue to have the normal prenatal care and testing. NIPT does not screen for open neural tube defects (ONTD). A detailed ultrasound at 18–20 weeks gestation offers the best detection rate for ONTD. Women who have Down syndrome screening via NIPT should be screened for ONTDs by detailed ultrasound. We previously recommended a blood test at 15 weeks, called alpha fetal protein (AFP). This screening for an ONTD should be limited to women with a BMI ≥40, or those with limited access to a quality 18 – 20 weeks ultrasound. These tests should be arranged by the physician providing prenatal care.
What is the cost?
Please refer to The Kelowna Regional Fertility Centre’s current fee schedule.
For further information about the BC Prenatal Genetic Screening Program, visit www.bcprenatalscreening.ca