What does a negative screening
test means?

A screening test is said negative when the
risk of having an affected baby is low (less
than 1/250) and does not justify the use on
an invasive diagnostic testing
(amniocentesis)

What does a positive screening
test means?

A screening test is said to be positive
when the risk of having an affected baby
is greater than 1/250.

Most of the time, the foetus is normal.
Detection rate and the risk of falsely
positive result may vary with the quality
of the test used. To confirm the result,
a diagnostic test is suggested
(amniocentesis / chorionic villous sampling)

The risk of foetal loss following amniocentesis or chorionic villous sampling is approximately 1/150.