A simple blood sample taken from the mother at any time from early pregnancy (10 weeks and onwards) can be analysed for cell free fetal DNA which can give a lot of information about the baby’s chromosomes.
The result of the simple “Harmony” blood test is predictive to more than 99% for Downs syndrome, 98% of Edwards syndrome and 80% of Patau’s syndrome, and so the introduction of this test will hugely reduce the need for invasive testing, and potentially miscarriage producing, CVS or amniocentesis. This is great news for couples because it totally eliminates the risk of procedure related to miscarriage.
It is important that an ultrasound scan is performed just before the blood test to confirm the pregnancy, and to check whether the mother is carrying twins (or more), although the test is not contraindicated in these cases.
Anyone who wants extra reassurance about the normality of the pregnancy can have the test. This includes those who are anxious as to know whether their baby has a chromosomal abnormality such as Downs, Edwards or Patau’s syndrome, older women (> 35 years) and those who have already had a chromosomally abnormal pregnancy.
The mother reads and signs a consent form. An ultrasound scan is performed, followed by a simple blood test from the vein in the woman’s arm, exactly the same as any other blood test. The tubes are immediately packaged in a special manner and sent to a lab in the USA.
The result is usually available within 12-14 days. There is a one in fifty chance that no DNA is obtained. This is not a positive or negative test: it is an unsuccessful test. In this rare occurrence an offer of a repeat test is made free of charge