Non-Invasive Prenatal Testing
About the Harmony Test
Did you know that about 10% of the DNA circulating in the blood of a pregnant woman is actually from the pregnancy itself? So, by taking a blood sample from the mother, it’s now possible to test for conditions like Down Syndrome in her unborn baby.
Developed in the USA by Ariosa Diagnostics, the Harmony Test is a non invasive blood test for pregnant women from 10 weeks of pregnancy. It has a 99% detection rate for Down Syndrome and will also identify most cases of Edward Syndrome and Patau Syndrome.
Who is it suitable for?
The Harmony Test is suitable for any pregnant woman with a singleton or twin pregnancy (except donor twin pregnancy).
Typically the test is useful for the following patients:
- Women over 35 who are concerned about their age related risk of Down Syndrome and other Trisomies.
- Women under 35 who want a safe, reliable, early and accurate test for Down Syndrome
- Women who have an increased risk or “High Risk” result from a Combined Test or Nuchal Translucency scan but wish to avoid unnecessary CVS or amniocentesis and their risk of miscarriage.
- Women who have an increased risk or “High Risk” result from a Triple test or Quad test but wish to avoid unnecessary CVS or amniocentesis and their risk of miscarriage.
- Women with a previous pregnancy with a baby with Down Syndrome, Patau Syndrome or Edward Syndrome
The test is not suitable for multiple pregnancies with donor eggs.
What does it test for?
- Trisomy 21 is the most common trisomy at the time of birth. Also called Down Syndrome, it is associated with moderate to severe intellectual disabilities and may also lead to digestive disease and 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.
- Turner Syndrome – a female fetus with a single X chromosome. These babies have a high risk of miscarriage and heart problems.
Can it tell my baby’s sex?
The test will also be able to determine the baby’s sex in most cases, with an accuracy of about 99%.
What is the chance the test will get a result?
Recent studies have shown that the failure rate for the test is affected by the mother’s weight as it affects the amount of fetal DNA available. Success rates are as follows:
Maternal Weight under 80kg – over 99%
Maternal Weight 80-100 Kg – 97%
Maternal Weight 100-120Kg – 93%
Maternal Weight 120-140Kg – 84%
Maternal Weight over 140Kg – 71%
What does a HIGH RISK result mean?
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. After the test, the number of women required to have a CVS or an amniocentesis 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 or 13 it does not mean that the fetus definitely has one of these defects , 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.
What does a LOW RISK result mean?
In the same way if the test results show that there is a LOW RISK that the fetus has trisomy 21, 18 or 13 it is unlikely that the fetus has one of these defects. However there is a very small risk that not all trisomy fetuses will be detected. All results should be interpreted by a clinician in the context of clinical and familial data: patients should continue with their usual scan appointments following testing.
How long will it take to get results?
Typically within 2 weeks but occasionally (3% of tests which are done) if there is not enough fetal DNA in the original blood sample then a repeat blood test may be required within a week of the original test at no extra cost.
Are there any risks to the pregnancy from the Harmony Test?
No. The testing is non-invasive: it involves taking a blood sample from the mother. The pregnancy is not put at risk of miscarriage, or from other adverse outcomes that are associated with invasive testing procedures such as CVS or amniocentesis.