The terms non-Invasive prenatal diagnosis (NIPD) and non-invasive prenatal testing (NIPT) refer to a relatively recent, ground breaking development in the field of DNA testing in pregnancy enabling medical specialists to collect DNA samples from the baby in an entirely safe and risk free manner. Prior to NIPT, expectant mothers had to rely on risky and invasive sampling methods that, although still commonly used today, pose certain, serious risks for the mother and the unborn baby. Invasive and non-invasive tests are both used to detect chromosomal abnormities in the unborn baby.
What are these risky invasive tests we are talking about?
There are 3 tests which can be classified under the heading of “invasive prenatal testing” methods.
Amniocentesis – is a procedure done by extracting a small volume of amniotic fluid from the amniotic sac which surrounds the fetus. The fluid is extracted by inserting a syringe through the abdomen. Click here to read more.
Chorionic Villus Sampling (CVS) – is a procedure done by extracting a sample of the chorionic villus (finger like protrusions on the placenta). The procedure is known as biopsy and it actually entails the removal of a piece of tissue. The tissue is removed either by insertion of a needle through the abdomen or a catheter through the cervix. Click here to read more.
Percutaneous umbilical cord sampling (also referred to as PUBS or Cordocentesis) – The procedure is very similar to amniocentesis and involves the insertion of a needle through the abdomen. However, whilst amniocentesis extracts amniotic fluid, percutaneous umbilical cord sampling extracts a blood sample directly from the fetus. It is the test that is carried out in a more advanced stage of pregnancy than CVS or amniocentesis.
All the above procedures must be done by a qualified medical professional and all 3 carry risks. These include:
- Blood loss from the puncture site
- Drop in fetal heart rate
- Premature rupture of membranes
Non-Invasive Prenatal Diagnosis (NIPD)/Non-Invasive Prenatal Testing (NIPT)
Non-Invasive Prenatal Diagnosis (NIPD): refers to actual diagnostic testing using maternal blood. The number of conditions that can be diagnosed is very limited. One example is achondroplasia.
Non-Invasive Prenatal Testing (NIPT): refers to a screening testing using maternal blood. A range of chromosomal abnormities can be detected but not confirmed which means further tests will be required in the case of a positive result.
Noninvasive prenatal testing analyzes cell-free fetal DNA circulating in maternal blood stream. The samples for the test can be collected via a normal medical blood draw which means the test does not even require the assistance of an OBGYN! Maternal blood will contain small quantities of DNA from the baby she is carrying. The cell-free fetal DNA (cffDNA) is detectable from 4-5 weeks’ gestation and comes from the placenta- a barrier between the fetus and the mother which actually allows some DNA to cross over. It is this fetal DNA that is found floating in the maternal blood that is extracted and analyzed in non-invasive prenatal testing.
The main advantage of NIPT is that it is 100% risk free for the mother and the baby. Unlike invasive tests which can cause leakage of amniotic fluid, miscarriage and other serious or unpleasant side effects. It is common belief amongst all those in the field of prenatal testing that the non-invasive prenatal test will become the standard method for establishing abnormalities in the unborn baby. However, there is still further research to be done although the test can accurately be used to detect Down’s syndrome and other abnormalities.
Noninvasive prenatal testing is now available, direct to consumer to detect birth defects as well as inherited diseases. Common conditions tested for include:
- Down Syndrome (Trisomy 21)
- Edward’s syndrome (Trisomy 18)
- Patau Syndrome (Trisomy 13)
The above are detected by analysis of non sex determining chromosomes. Some companies also include sex chromosome abnormalities by analyzing the X and Y chromosomes.
Companies offering the test will send a kit directly to the person qualified to take the blood samples. The expectant mother will just need to turn up on the day of the appointment and have her blood samples collected. Once done, they need to be sent to the laboratory.
NIPT testing: It is a screening test not a diagnostic test
Whilst NIPT testing is considered very accurate and reliable, it is essentially a screening test which does not provide as conclusive a result as a diagnostic test like amniocentesis. This is a very important difference between tests like CVS, amniocentesis and cordocentesis and the NIPT test. If results of NIPT testing are negative, the expectant mother can have her mind at rest that her baby will not suffer from the diseases tested for. If results are positive, further tests will most probably be needed to confirm whether the condition is present in the unborn baby.
Price of Noninvasive prenatal testing and laboratories
The pricing for NIPT testing varies from laboratory to laboratory. Different laboratories may test for different conditions which could be one of the factors affecting the price.
Most laboratories offering the test are based in the USA although there are some laboratories in the UK as well as other parts of the world.