Second Trimester Screening
This is done between 15-21 weeks and is a blood test to measure the amounts of b-hCG (beta subunit of human chorionic gonadotrophin), AFP (serum alpha fetoprotein), uEst (unconjugated estriol) and Inhibin A.
A high level of hCG and low levels of AFP and uEst can detect a higher risk of having a Down syndrome baby. The test is also called as triple screen.
Integrated Test
The most effective test for Down syndrome is Integrated test which combines the NT test and blood test of first trimester with the triple screen test of the second trimester. There are 94% chances of Down syndrome detection when tests are combined.
Diagnostic Tests
If your screen test results in positive, then you can opt for diagnostic tests. Currently there are two tests CVS (Chorionic villus sampling) and Amniocentesis.
CVS
This test is done during the first trimester to obtain the cells from placenta which is similar to the fetal cells. The cells are analyzed for the extra 21 chromosome.
Amniocentesis
This test is done during the second trimester to obtain the amniotic fluid surrounding the fetus. This also checks for the presence of extra 21 chromosome.
As Down syndrome can affect an entire family, it is good to go for such Down syndrome tests. As older women over the age of 35 are more at risk than younger mothers, such tests are necessary for them to know the health of the developing baby.
