Maternal Serum Screening Test
All women, whatever their age, have a small risk of delivering
a baby with physical and/or mental disability. In some cases
the disability is due to chromosomal abnormalities such
as in Downs Syndrome. Downs Syndrome is a chromosomal disorder
caused by the presence of an extra chromosome 21 (trisomy
21) in the cells of the developing fetus which can manifest
in children with varying degrees of mental disabilities,
congenital heart diseases, gastrointestinal abnormalities,
poor muscle tone etc. This is known to occur in 1 in every
600 pregnancies around the world. About
50% of the fetuses with Downs syndrome abort and 50% of
them will survive to delivery.
As the maternal age increases the relative risk of having
a baby with Downs syndrome increases, the risk doubles at
maternal age of 35 years. Hence screening
tests should be offered to all pregnant women.
Screening test can be done in the First
or Second trimester
First trimester screening test (FTS) or the Combined test
which is done between 11-14 weeks is unique as it involves
a combination of ultrasound (nuchal translucency)
and a maternal blood test to identify biochemical
markers (Beta HCG and PAPP A – double markers) in conjunction
with maternal age. This helps in picking up 90% (I.e. 9
out of 10 cases) of Downs syndrome.
