The Haute Autorité de Santé recommends non-invasive screening tests

We have been talking about it for at least ten years: a maternal blood test could be as reliable as an amniocentesis to detect trisomy 21. It is in this case to spot an overrepresentation of fetal DNA sequences from chromosome 21 within the fetal DNA that circulates in small amounts in the mother 's blood . The Haute Autorité de Santé (HAS) published on November 18, 2015 an assessment on the relevance and reliability of these tests. Conclusion: the trisomy rate detected is greater than 99%

How is trisomy 21 currently detected?

Currently trisomy 21 screening is based on a triple test at the end of the first trimester (between 11 and 14 weeks of amenorrhea):

- A blood test that measures biological markers and thus assesses a risk of less than or greater than 1/250. Nothing to do with taking blood from the baby's DNA tracking, so.

- This blood test is coupled with an ultrasound that measures the nuchal translucency : the thickness of the fetal neck which we know that the thicker it is (more than 3mm), the more the risks of trisomy increase.

- The third factor taken into account is the maternal age : the older one is, the more the risk of trisomy 21 increases.

Depending on the results of this triple test, an amniocentesis is proposed to diagnose, ie to have a reliable answer. But this examination which consists in taking amniotic fluid by inserting a needle by the abdominal route is not without risk. In less than 1% of cases, a miscarriage can occur in the days that follow.

How to benefit from new non-invasive screening tests?

Although we have been talking about it for several years, maternal blood tests measuring fetal DNA are not yet easy to obtain when we are pregnant. The few hospitals that offer it , such as the American Hospital in Paris, send their samples to Switzerland. In France, the CERBA laboratory is a pioneer in the sector . Last year, CERBA lowered the price of its test to make it accessible. It is now necessary to pay about 300 €, not reimbursed by social security. But, pending the outcome of other ongoing studies, the HAS recommends - even if these results are positive - to confirm the result of the test by amniocentesis.