By Nanda Cathy Leung
In March 2016, the Dutch Health the intention to allow all pregnant women to access non-invasive prenatal testing (NIPT), a blood test screening method for chromosomal abnormalities in unborn children. For the last two years in the Netherlands, the NIPT test has been offered only to a selected group of high-risk expectant mothers. Now, however, as long as there is agreement from the Health Council, the test should be available in the basic heath insurance package from 1 January 2017, meaning it will be offered to all pregnant mothers. So what is the NIPT test?
The NIPT blood test examines a pregnant mother’s blood, which also includes DNA fragments from the baby. The placenta is a two-way street with biological matter passing in both directions; from mother to baby but also from baby to mother. From the tenth week of pregnancy there is enough DNA from the baby in the mother’s blood to enable testing for the presence of a chromosome disorder. The DNA is specific to the current unborn pregnancy only, as after birth these fragments of the baby’s DNA leave the mother’s bloodstream within a few hours. The test is known to be 99% accurate and the procedure is just a simple blood test. The blood is sent away to be tested in a specialist laboratory, and the results are usually available after one to two weeks. Chromosome conditions A baby born with Down’s syndrome (trisomy 21) will have an extra copy of chromosome 21 in each cell and may have some learning differences, the level of which could range from mild to severe. In addition, some health problems are more common in people with Down’s syndrome. Though the most common chromosome disorder is Down’s syndrome (trisomy 21), the NIPT test is also able to detect the rarer and more serious conditions; trisomy 18 (Edwards’ syndrome) and trisomy 13 (Patau’s syndrome).
At present in the Netherlands, the NIPT test is only offered to pregnant women who have an increased risk of having a child with a chromosome abnormality. The combinatietest (combination test) – which includes a blood test and nuchal translucency (NT) scan – is used to identify women with this increased risk but there can also be other reasons for recommending a NIPT test. Before the NIPT test was developed, if a high risk of a chromosome abnormality has been determined, pregnant mothers would have been offered one of two invasive diagnostic tests: chorionic villus sampling (CVS) or amniocentesis. A CVS test requires a small piece of the placenta which is obtained via a tiny needle inserted through the pregnant mother’s tummy. An amniocentesis test requires a small sam-ple of amniotic uid from the womb (uterus) which is obtained in the same manner. With the advent of NIPT, the CVS and amniocentesis tests have not been made obsolete. The NIPT test for Down’s syndrome is over 99% accurate but there is still a small chance that the result will be incorrect, and because of the very small chance of an incorrect result, if there is a positive NIPT result, pregnant women will then be offered an invasive diagnostic test (amniocentesis or CVS) to confirm the result.
For and against
The NIPT test has been hailed as a means to test for chomomsome abnormalities in a pregnancy without the need for an invasive procedure. Whereas the CVC and amniocentesis tests both carry a small risk of miscarriage, the NIPT test has no such risk so it might be hoped that increased use of the NIPT test might mean fewer miscarriages. Elsewhere, the UK is also facing calls to widen access to the NIPT test on the NHS. In the Netherlands, this announcement from Schippers has not been welcomed by everyone. There is concern that this development will lead to a society without Down’s syndrome, with an increased social pressure to abort pregnancies testing positively for trisomy 21.
One mother shares her experience of NIPT: “During my first pregnancy, the combinatietest showed an increased risk of my baby having a genetic disorder. I opted for a CVS to find out for sure, but it was worrying knowing that the procedure carried a small chance of miscarriage. Also, having a needle inserted into my pregnant belly gave me an awful feeling no matter how skillfully it was done. A few days afterwards we were given the devastating diagnosis for trisomy 18: I would likely lose the baby. After going through that, a year later, when pregnant again, at ten weeks I was offered the new NIPT test without even waiting for a combinatietest. A simple blood test seemed a much better option for me; and could be performed comparatively earlier than the other tests. We had hoped this would be less stressful but sadly, the NIPT test also detected a genetic disorder; Down’s syndrome. A further, invasive test was scheduled to check this, during which the medical staff were able to see that the baby’s heartbeat had stopped; the baby had already died.
A third pregnancy led to another NIPT test and that time, the test found no chromosome abnormalities. Having gone through the accompanying emotions and physical discomfort of a CVS previously, I certainly valued the opportunity to get a diagnosis earlier in pregnancy and at no risk to the baby. However easy the test is, though, it certainly doesn’t make it make it any easier to deal with if the result is not the one you were hoping for.” www.meerovernipt.nl (in Dutch)
www.rapid.nhs.uk (for UK patients)