Shared blood through the placenta
DNA testing of the fetus is not new; it has been around since about 20 years ago, using samples of amniotic fluid / chorion for testing. However, DNA testing of the fetus using the mother`s blood sample is fairly recent, and can be done from as early as the 8th week of pregnancy. There are those that are wary of it as a new procedure.
Let`s explore the theory behind prenatal DNA testing of the fetus using a blood sample from the mother.
A mother and their unborn baby are connected via the placenta, and it is commonly known that a fetus receives oxygen and nutrients from the mother through this connection.
Approximately fifteen years ago, since fetal DNA was first discovered to be present in the mother`s blood, it has been posible to use that DNA for genetic testing to confirm genetic diseases and congenital diseases. Prenatal paternity DNA testing using the mother’s blood started to be done about 10 years ago, and although the accuracy was low, the price was rather expensive. It wasn`t until 2013 that highly accurate prenatal paternity DNA testing began to be available.
Why testing is possible from the 8th week
In general, it is possible to do prenatal paternity testing from the 7th or 8th week of pregnancy as the amount of fetal cells present in the mother`s blood increases. The amount of fetal cells detectable in the mother`s blood can differ from person to person, with cases of successful DNA tests as early as 6 weeks being reported, as well as unsuccessful DNA tests at 14 weeks. There are large differences between individuals.
Overseas there have even been reports of test being unsuccessful from the 24th week of pregnancy.
As testing is done with just 10ml of blood for the mother`s sample, it is recommended that sample collection be done from at least the 8th week of pregnancy.
In the event that not enough DNA can be obtained from the mother`S blood sample, we offer to do a free re-test. So far there has not been a case where we were unable to obtain a result from a re-test.
DNA tests that are safe even for babies
Previous prenatal DNA tests using amniotic fluid pose the risk of harming the fetus and/or causing a miscarriage. That being the case, there are few hospitals that will collect amniotic fluid for the purpose of a paternity test.
Althought the cost of a prenatal paternity test using amniotic fluid is cheaper than a non-invasive prenatal paternity test using a blood sample, as the procedure for collecting amniotic fluid is an additional 100,000 or so, in the end there is really no benefit to choosing this method in terms of cost.
More than 99.5% of prenatal DNA test conducted in recent years have been non-invasive using a mother`s blood sample. Having a paternity test done after the baby has been born is the most affordable method of paternity test, but if you need to find out who the father of the baby is before it is born, then we recommend have a prenatal paternity test done with a blood sample.