The test’s efficiency was monitored on 6,388 pregnancies and the results have been published in Genetics in Medicine. In 2013, the group had already announced their role in developing the algorithm behind the same test to detect frequent chromosomal anomalies – such as Down syndrome for example – in foetal DNA which was directly extracted from the mother’s blood. The test offered rapid and safe results, while revolutionizing prenatal testing. This enhanced version could be extended to detect anomalies that are rare and severely disabling.
Various chromosomal anomalies – such as the commonly known trisomy 21 or Down syndrome – can be detected in foetal DNA which has been extracted from a pregnant mother. However, foetal DNA extracted from the placenta, such as is the case in amniocentesis can be dangerous both for the baby and the mother. Though present in trace amounts, foetal DNA is also found in the mother’s blood, and the extraction of this cell-free DNA is safe. It is on this premises that non-invasive prenatal tests were developed.
“The first NIPTs were implemented for the common foetal chromosomal anomalies, such as trisomies 21, 18 and 13, and to a lesser extent a few sex-chromosome anomalies, explains Ioannis Xenarios. However, it became apparent that several foetal chromosomal anomalies were being missed because they could not be detected.”
Amongst these are rare autosomal trisomies, a few structural chromosome anomalies, and some placental trisomies which account for a low but significant risk. As an example, one rare pathogenic chromosomal anomaly known as T22 mosaicism could be missed by the ‘basic’ version of the NIPT – which is reimbursed by the health insurance.