Screening for trisomy 13, 18 and 21 by analysis of free circulating foetal DNA
What is NIPS?
During pregnancy, the placenta releases detectable foetal DNA into the maternal bloodstream. If DNA from chromosomes 13, 18 or 21 is present in abnormally high quantities, this means that the foetus has a high probability of having a trisomy for one of these chromosomes. NIPS thus makes it possible to detect trisomy 13, 18 or 21 in the foetus by means of a simple blood test on the mother-to-be. It is a test with no risk for the foetus.
What are the indications?
NIPS can be carried out during each pregnancy in the absence of ultrasound anomalies. It is covered by the CNS on medical prescription. The NIPS test does not replace regular ultrasound monitoring during pregnancy, regardless of the result.
This test will be prescribed by the gynaecologist or midwife who is monitoring your pregnancy. NIPS can be carried out as early as 10ᵉ weeks of amenorrhoea, ideally from week 12, but it can be prescribed until the end of the pregnancy. Blood samples are taken without an appointment in all our laboratories, and also by appointment at the address of your choice, from Monday to Saturday.
It is not necessary to be fasting. Please bring your prescription, consultation certificate and signed consent form.
What tests are available?
What is the performance of the test?
This test is very sensitive (>99.9%) and very specific (99.9%) for detecting trisomy 13, 18 and 21. Nevertheless, only amniocentesis allows a definite diagnosis. It will be proposed to you according to the results of the NIPS.
How to interpret the results?
The results will be communicated to you by the prescriber. If the result is negative, this means that the test did not detect foetal trisomy 13, 18 or 21. The usual monitoring of your pregnancy will continue.
If the result is positive, the presence of trisomy (13, 18 or 21) is likely. A positive result must be confirmed by an invasive prenatal diagnosis such as amniocentesis.
If the result is inconclusive or uninterpretable, this does not mean that the risk of trisomy is high, but simply that due to a technical problem or too little foetal DNA, the test has failed. It is then necessary to repeat the analysis on a new sample, usually 14 days after the first test.