Non invasive prenatal paternity testing is a means of establishing paternity that does not require an invasive sampling procedure. Unlike amniocentesis or chorionic villus sampling (considered to be invasive), non invasive prenatal tests only require blood samples from the alleged father and mother. On the other hand, with invasive tests, a fetal DNA sample is required that is taken from inside the womb and to get the necessary sample for the test, a needle is inserted within close proximity of the baby- this means that there have been cases where the needle has harmed the unborn baby or even led to miscarriages.
Non invasive testing is possible because a pregnant mother carries traces of her unborn baby’s DNA in her blood. Researchers have known this for a long time but have been unable to successfully extract this DNA from the maternal blood stream. The most accurate and reliable prenatal paternity tests use cell free fetal DNA; there are other non invasive prenatal tests which use the entire fetal cells, rupture the cell and extract the fetal DNA from with the cell nucleus- these latter tests can be less accurate and sometimes carry the risk of misdiagnosis due to previous pregnancies. Cell free fetal DNA tests analyses what are known as Single Nucleotide Polymorphisms or SNPs. These SNPs are locations on the human genome where a single base pair varies between individuals. Non invasive prenatal paternity testing that use cell free fetal DNA in the maternal blood; analyze hundreds of thousands of these SNPs.