Invasive and Non Invasive Prenatal Paternity Testing

Invasive and non invasive prenatal paternity testing enables one to determine paternity before the birth of a child. In some countries, getting the test done is easy, but in other countries such as Ireland and France getting a prenatal test done for paternity testing is difficult because of the ethical issues that abound.

 

The DNA sampling procedures for prenatal paternity testing can either be invasive or non invasive. Non invasive prenatal paternity testing is quite a new field of genetic research and most often you will find companies offering invasive prenatal testing procedures.  Also, generally, invasive prenatal tests are also used as diagnostic tests to reveal any chromosomal abnormalities or hereditary illnesses in an unborn baby. These can include:

•Anencephaly
•Down’ syndrome
•Rare, inherited metabolic disorders
•Spina bifida and other structure problems

Non Invasive prenatal testing for paternity

It is today possible to carry out a non invasive prenatal paternity test using a medical blood draw of the mother’s blood. Some companies are also offering this test with just a few drops of blood taken using a lancet provided in a kit- the quantity of fetal DNA using a finger prick might be too low however, to conclude the test.

The science behind the test relies on the fact that fetal DNA fragments find their way into the mother’s blood stream through the placental wall. It is possible for scientists to isolate these DNA fragments to carry out a paternity test. There is one particular vein that scientists have found is particularly rich in fetal DNA. Non invasive prenatal testing carries a huge advantage over non invasive testing in that it is totally risk free.

The concentration of fetal DNA in the mother’s blood ranges anywhere between 3- 13% in any given maternal blood sample- for a scientific perspective, this is considered to be a pretty high concentration of fetal DNA. Once the DNA is extracted, the non invasive prenatal paternity test will accurately establish whether the tested father is the biological father of the unborn child.

The following are the two invasive procedures required to extract a DNA sample from the mother’s womb :

Prenatal paternity testing using Amniocentesis

Under general or local anesthetic, an obstetrician is required to extract a sample of amniotic fluid from the amniotic sac which envelopes the unborn child. Fetal urine, fragments of fetal DNA and proteins freely move in the amniotic sac.

The test is carried out anywhere between the 15 and the 20th week of pregnancy. The exact location of the baby is found using an ultra sound and the surgeon overseeing the procedure will insert the needle into the abdomen guided by the ultrasound. A clear, amber-coloured amniotic fluid is extracted. The volume of fluid varies depending on whether the sample will be used for prenatal paternity testing or to screen for genetic diseases.

Both invasive prenatal paternity tests carry the risk of miscarriage. With amniocentesis there is also the possibility of damaging the baby’s limbs.

Prenatal paternity testing using Chorionic Villus Sampling

Chorionic villi are tiny finger-shaped structures which line the placenta. Inserting a thin tube into the vagina will suffice to collect a DNA sample or rather, a sample of the chorionic villi. The procedure is thus, a bit different to amniocentesis as it does not require entry to the abdomen and involves an entirely different sample. An ultra sound is still nevertheless needed to guide the catheter to the correct place. CVS can be done earlier in pregnancy, in fact around the 10th week.

As with any invasive procedure there are certain risks. The risks and side effects with CVS include any of the following:

• Miscarriage
• Cramping
• Fevers and chills
• Leakage of amniotic fluid; if the amniotic fluid levels fall too low the baby’s life may be seriously endangered.

Another option besides prenatal paternity testing is to wait for the birth of the child- a paternity test can be carried out at the moment of birth with a DNA sample taken using an oral swab.