Harmony is a non-invasive prenatal test that screens for chromosome abnormalities as early as week 10 gestation.
The test is preformed like any routine blood draw. This is because around 10% of cell-free DNA (cfDNA) in a pregnant women’s circulation originates from the fetus. Analyzing the blood sample at a genetic laboratory enables separating fetal genetic material and testing it for various chromosome conditions.
The Harmony test screens for common chromosomal abnormalities (known as trisomies), and sex chromosome aneuploidies such as triple X syndrome, Klinefelter’s syndrome, and more.
Among the common conditions screened in a Harmony test:
Down syndrome – this disorder’s frequency is around 1 in 700 births. Symptoms include intellectual disability, shortened life span and various heart and gastrointestinal defects.
Edwards syndrome – this disorder occurs in around 1 in 5,000 live births. Symptoms include heart defects, profound intellectual disabilities, and early death. Many of the affected pregnancies end prematurely.
Patau syndrome – occurs in around 1 in 16,000 live births. People with this disorder have a short life expectancy, symptoms include profound intellectual disability and multiple anatomical defects.
The test’s accuracy rate changes according to the disorders tested. The highest accuracy rate is for Down syndrome, it is shown to accurately identify over 99% of cases of Down syndrome.
The test can identify over 98% of trisomy 18 cases (Edwards syndrome), and over 80% of trisomy 13 (Patau syndrome) cases.
It should be noted that other prenatal tests, such as amniocentesis or CVS, offer a higher accuracy rate in detecting chromosome abnormalities, but these are invasive tests that come with a risk for complications and miscarriage. For this reason, women are asked to sign a form stating they are aware of these risks before undergoing the tests.
The Harmony test is considered safe and poses no risk to both mother and fetus.
What can be learnt from this test?
Results show one of two possible answers for each disorder – “low probability” or “high probability”. A “low probability” result is not a 100% confirmation that the fetus does not have the disorder but means that most chances are that the fetus has not developed this condition.
However, “high probability” results require a referral to genetic counselling and further prenatal tests to confirm the diagnosis.
Among the tests recommended after receiving high probability results are chorionic villus sampling or amniocentesis.
The test can also be performed in twin pregnancies.
What conditions does the test not detect?
There are hundreds of disorders caused by genetic mutations known to medical research today. However, not all these conditions are related to the chromosomes.
In addition, the Harmony test does not diagnose all existing chromosome abnormalities.
Moreover, certain birth defects are not caused by genetic or hereditary factors. For this reason, further tests are required for diagnosing fetal genetic disorders. Some of these tests are non-invasive while others are invasive.
For example, the Harmony test cannot detect disorders resulting from lack of oxygen to the fetus, or conditions caused by infection or exposure to certain toxins.