Invasive Testing includes
Second trimester screening test can be the triple
screen test (TST) or the quadruple test is usually
done between 15-21 weeks. The sensitivity of this test is
only 60 % (ie it detects 6 out of 10 cases) but still offered
to women who are booked later in pregnancy.
Screening tests interprets only the relative risk for the particular chromosomal disorder in the present pregnancy and this is not a confirmatory diagnostic test. The result of the screening test will read as screen positive or screen negative.
They denote whether the pregnant women
is either at high risk or low risk respectively for carrying
a pregnancy with Downs syndrome. The high
risk women can then be subjected to more definitive invasive
testing which involves direct fetal sample testing.
