Prenatal screening is a very complex process that begins with a well done and well interpreted echography of the fetus.
From the echography the doctor must detect the presence of nuchal translucency and a evident degree of the nose ossification.
These two parameters suggest that there are a high probabilities of a genetic anomaly presence in the fetus.
The next step is to confirm the echography diagnosis and then make a very invasive test such as an amniocentesis or villocentesis that will give an answer with a very high percentage of safety.
These tests are very invasive because go to take genetic material directly into the amniotic sac, they are not very attractive and carry a risk of abortion approximately every 200 cases.
With the recent tests evolution is possible to avoid this complicated methodology of the good interpretation of echography and invasive tests.
Today is possible to determine very safely the fetus genetic anomalies, through a mother blood test.
In fact cause the mother fetus placental interchange the mother blood contains the cells of the fetus which can be identified and from these can be detected the genetic composition.