+353 (1) 685 6929 The new non-invasive Paternity Test has shed a light on a new era of DNA testing in the prenatal stage. With the possibility to establish paternity at 10 weeks of pregnancy and in a risk free way, this test has proved indeed a huge leap forward from other more conventional DNA tests.
Why the Placenta is Important
The purpose of the placenta is for the mother to exchange oxygenated blood and deoxygenated blood and moreover, also to provide nutrition to ensure healthy development. It also removes the baby’s waste and is the interface between blood supplies of the mother and her child.
On the mother’s side of the placenta, it is possible to separate the mother’s plasma from the rest of her blood by taking a blood sample from her body – usually her arm. Both baby’s DNA and the mother’s DNA are present in the plasma at a level of around 15% after week 12 – though there is sufficient at week 10 for an accurate test.
Because the DNA obtained from the placenta is not always in the form of complete DNA strands, a technique has been developed to identify genetic variations between individuals known as SNPs (‘snips’) or Single Nucleotide Polymorphisms. These can be used as genetic markers in DNA fragments. Others methods, including include ‘Short Tandem Repeat’, or STR analysis, require completely intact DNA molecules.
Free and Cellular DNA
Fragmented strands of fetal DNA can be used to detect these SNPs, and use them to determine paternity. The importance of this technique lies in the definition of free fetal DNA and cellular DNA. Most DNA contained in a mother’s blood is cellular, meaning that it is contained within a body cell. The problem with this is that cellular DNA is stable, and can remain within the body for a number of years.
That means that the cellular DNA of a woman who has had previous children will be liable to contain the DNA of her child for several years, and any test carried out using this cellular DNA will be liable to misinterpretation.
By using ‘cell-free’ fetal DNA that is not bound up in any of the mother’s body cells, one can receive results without any ambiguity – meaning that misdiagnosis is not possible, and that results are as accurate as the test method rather than being compromised by the origin of the sample.
Prenatal Paternity Testing
It is only this specific test that uses cell-free fetal DNA in prenatal paternity testing, others using cellular DNA that cannot possibly offer reliable results. There is no question about the accuracy of these results, just whose DNA is being tested – your current baby, or one that was born to a different father a year or two ago? This is not uncommon with women who divorce, remarry, and have children with their new husbands.
Both cellular DNA and that which is circulating freely in the mother’s bloodstream can be used to compare with the DNA of the prospective father. However, in one case, the relationship can be denied, while in the other in can be proved. It is of extreme importance that only the DNA from the current fetus or baby is used for such a test, and the only way to ensure that is to use the free DNA in the mother’s blood that has only recently been passed on by the placenta.
Cellular DNA does not meet this criterion, and should be avoided when carrying out non-invasive prenatal paternity testing. If you test involves cellular DNA (ask the question) then do not take it – it will not be relevant, and you could never be sure which baby’s DNA was being tested. Highly accredited laboratories carry out the non-invasive prenatal paternity test that does not involve this ambiguity, cannot misdiagnose, and is over 99% accurate while being 100% safe to your developing child.