Harmony Prenatal Test
See our FAQs for more information
* The pregnancy must be over 10 weeks gestation otherwise the blood test will not be performed.
With the advances in genetic medicine cell free foetal DNA which is present in the mother’s blood from early pregnancy, can now be used to sequence the DNA of the baby to check for genetic abnormalities. This is as simple as taking a blood sample from the mother and it being sent away for lab testing. This is huge leap in genetics testing as this test only requires a simple non invasive blood sample from the mother.
The Harmony test can be performed from 10 weeks gestation. The test includes an ultrasound which is performed prior to the bloods being taken. The purpose of the scan is to date the pregnancy, check that it is a viable pregnancy and also check for the presence of two or more foetuses.
The Harmony test is the most frequently performed non-invasive prenatal test which uses ‘targeted sequencing’ where they analyse fragments from specific chromosomes, this targeted analysis gives an accurate risk assessment of trisomy 21, (Down’s Syndrome) 18 (Edwards Syndrome) and 13 (Patau Syndrome.)
With Harmony there is also the option to test for abnormalities of the sex chromosomes, there is normally 2 sex chromosomes either XX – female or XY – male. However abnormalities arise when you receive 1,3, or even 4 chromosomes. Monosomy X is where you only receive one X chromosome, this is also know as Turners Syndrome. Trisomy of the sex chromosomes is where you receive three chromosomes either XXX (Triple X syndrome) or XXY also know as Klienfelters syndrome. It is also possible to receive 4 sex chromosomes XXYY.
For more information on the Harmony test see our Frequently Asked Questions Page.
Conventional Down’s Syndrome Test
The current NHS screening tests for Down’s syndrome are the “Combined test” or the “quadruple test”. The combined test is carried out between 11 and 14 weeks, which involves a Nuchal Translucency scan and blood test. The Nuchal Translucency scan measures the length of the nuchal fluid at the nape of baby’s neck, the greater the extent of the nuchal pad the greater the risk of abnormality. The blood test measures serum markers in the blood; these are then used along with factors such as maternal age, weight, family origin and gestation of the pregnancy to determine the risk of having a Down’s syndrome baby.
The quadruple test is carried out if you are too far on in pregnancy to have the combined test, this test is a blood test with looks for markers in your blood these markers are used along with maternal age, weight and gestational age to calculate your risk factor of having a down’s Syndrome baby. This is either low risk or high risk. High risk patients will be invited for a diagnostic test such as chronic villus sampling (CVS) or amniocentesis which both come with a risk of miscarriage. There is a 5% false positive rate with these conventional tests, which is much higher than the false positive of the harmony test which is less than 1%, which means with harmony there is less chance of having to have a follow up invasive procedure.
See our FAQs page for further information.