The Procedure itself…
Nuchal translucency test
& Blood test - stage 1
• Cold gel is applied on your abdomen
• A scanner moves over your skin with some pressure
at certain points
• The captured images on the screen are explained
by the technician to you
• The nuchal translucency is measured along with
other indicators such as structural heart problems,
shortened femur length (a bone in the leg), webbing
between fingers
• There is also a possibility of looking at the
fetus face to check for the presence of the nasal bone
• Baby's length will be assessed to confirm the
due date
• The more indicators found, the higher the chance
of following up with an amniocentesis
• A sample of your blood is taken at this stage
to measure the concentration of 1 marker - pregnancy
associated plasma protein-A.
• You will be given an appointment date for the
second stage of the test
Blood test - stage 2
The second blood sample is taken at 14 weeks and not
later than 20 weeks
This sample is to measure the concentration of 4 markers:
1. Alpha-fetoprotein (AFP)
2. Free B-human chorionic gonadotrophin
3. Unconjugated estriol
4. Inhibin-A
A single screening result is derived by integrating
both the stages. The nuchal scan measurement, your age
and the levels of 5 markers (obtained from both the
stages) are used to estimate your risk of Down's syndrome.
The detection rate is 85%. The level of AFP in the second
blood sample is used to predict if there is an increased
risk of spina bifida or anencephaly. FYI, if AFP is
abnormally low, it may suggest the baby could have Down's
syndrome. It is important that both the ultrasound and
blood sampling be done together to produce greater accuracy.
