Harmony Test (Non Invasive Prenatal Testing, NIPT)
Non-invasive prenatal testing (NIPT) analyses cell-free DNA circulating in the pregnant mother’s blood. It is a new option in prenatal screening for Down’s syndrome (trisomy 21) and other common chromosomal conditions (trisomies 18 and 13) and X and Y chromosome conditions.
This test can be requested for any singleton pregnancy, including in vitro fertilization (IVF) pregnancies with egg donors. It can now also be requested for ALL twin pregnancies (without X or Y) conceived naturally or by IVF using the patient’s own egg or a donor egg.
About the Harmony Test
DNA from the fetus circulates in the mother’s blood. Cell-free DNA (cfDNA) results from the natural breakdown of fetal cells (presumed to be mostly placental) and clears from the maternal blood within hours of giving birth.
During pregnancy, cfDNA circulating in a mother’s blood can be tested to estimate the chance of a fetus having a chromosomal condition sometimes called a trisomy. This occurs when there are three copies of a particular chromosome instead of the expected two. The test looks to detect the following :
- Trisomy 21 (Down’s syndrome) is the most common trisomy at the time of birth. It is associated with moderate to severe intellectual disabilities and may also lead to digestive disease, congenital heart defects and other malformations.
- Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome) are associated with a high rate of miscarriage. These babies are born with severe brain abnormalities and often have congenital heart defects as well as other birth defects. Most affected individuals die before or soon after birth, and very few survive beyond the first year of life.
- Sex chromosome conditions. The sex chromosomes (X and Y) determine whether we are male or female. X and Y chromosome conditions occur when there is a missing, extra, or incomplete copy of one of the sex chromosomes. The Harmony with X, Y test can assess risk for XXX, XYY, XXYY, XXY (Klinefelter syndrome), and a missing X chromosome in a girl (Turner syndrome).
There is significant variability in the severity of these conditions, but most individuals have mild, if any, physical or behavioural features. If the mother is interested in having this optional testing, she should talk with her healthcare provider to determine if it is right for her.
Please note sex chromosome testing is not available for twin pregnancies.
How is the test taken
The test involves taking a blood sample from the mother after ten weeks of pregnancy.
How accurate is Harmony?
A ‘high risk’ result is indicative of a high risk for a trisomy. The test identifies more than 99% of fetuses with trisomy 21, 98% of fetuses with trisomy 18, and 80% of fetuses with trisomy 13, and 96% of fetuses with Turner Syndrome. X and Y analysis provides >99% accuracy for fetal sex. Accuracy for detecting other sex chromosome anomalies varies by condition.
After the test, the number of women offered a CVS or an amniocentesis on the strength of this test is less than 1%.
It is important to note that if the test results show there is a high risk that the fetus has trisomy 21, 18, 13 or sex chromosome conditions, it does not mean that the fetus definitely has one of these conditions, although it is highly likely. For this reason, in the event of a ‘high risk’ (or positive) result, follow-up testing by an invasive procedure is recommended.
In the same way if the test results show that there is a ‘low risk’ that the fetus has trisomy 21, 18, 13 or sex chromosome conditions, it is unlikely that the fetus has one of these conditions. However, there is a very small risk that not all trisomy fetuses will be detected. All your results will be interpreted by our experienced Fetal Medicine Consultants in the context of clinical and familial history.