The objective of this project is to develop a non-invasive prenatal diagnostic test for
trisomy 21 which is reliable, sensitive and cost-effective, and thus, offers an alternative
to the currently employed invasive diagnostic tests amniocentesis and chorionic villus
Current prenatal screening methods (blood markers and ultrasound) for trisomy 21 (Down
syndrome) detect about 90 % of cases and have a false positive rate of > 90 %. The results of
these tests are expressed in risks for trisomy 21, the threshold being in France at 1/250.
Women exhibiting a higher risk are offered to undergo invasive diagnostic testing, either by
amniocentesis or chorionic villus sampling. However, these invasive diagnostic methods are
associated with a considerable risk of miscarriage (1-3 %), and thus underline the importance
to develop a safe and non-invasive prenatal diagnostic test for trisomy 21. The investigators
have planned to assess the clinical impact of a non-invasive prenatal method to detect
Trisomy 21 through genetic analysis of circulating trophoblastic cells.