Up until recently there were just two methods for extracting fetal DNA from a pregnant woman. Both these two methods are considered risky to some extent or other and moreover, both have side effects. Let’s take a brief look at each one to understand more:
Chorionic Villus sampling: this prenatal DNA test is carried out at around 11 weeks of pregnancy. The OBGYN overseeing the procedure can either extract samples of fetal tissue by inserting a catheter through the vagina or by inserting a needle through the abdomen. The tissue collect is specifically known as chorionic villus.
Amniocentesis: This test in pregnancy is carried out at around 13 weeks of pregnancy. To be able to extract a sample of fetal DNA the OBGYN must insert a needle through the pregnancy belly and extract around 20ML of amniotic fluid (the liquid which surrounds the unborn baby in the embryonic sac).
The risk of miscarriage is slightly higher with chorionic villus sampling that with amniocentesis. Besides this risk (although very small), the tests have side effects which can be unpleasant. Fever, chills and soreness are not uncommon. Luckily, the past decade has seen the emergence of non invasive tests which have none of the above risks or side effects.
Non Invasive prenatal testing
Fetal DNA for this test is extracted from maternal blood. There is no need to go anywhere near the womb and blood samples for this test are in fact collected just like any other blood draw- usually from the vein. The test can also be carried out at only 10 weeks of pregnancy, thus earlier than both amniocentesis and chorionic villus sampling. Read more about our non invasive prenatal paternity test.