The blood taken from the mother is tested for the levels of three (hence 'triple test') specific proteins; AFP, HCG and UE3.  Details of these are described on the following page.  The levels of these markers combined with the mother's age and the ethnicity of the parents can indicate the probability of the foetus having certain genetic disorders.

History:  

Previously, a single screening for AFP was used to both detect Open Neural Tube Defects and allow high risk mothers (women over 35 years old) the chance to find the probability that their child had the disorder Trisomy 21 (Down Syndrome).  The introduction of the two other markers was first intended to increase the effectiveness of these tests.

Now however, the Triple Test screening process has been refined to include testing for the following (the actual screening results provided varies between different countries and clinics) :

• Down Syndrome (Trisomy 21)

• Neural Tube Defects (Spina Bifida)

• Ventral Wall Defects

• Can identify Women carrying twins

• Can identify pregnancies more or less advanced than thought

• Can identify some women that have a risk of premature birth

• Can identify some foetuses that risk a low birth weight

• Some screening agencies now also produce a probability pattern for Trisomy 18 (by using free b-hCG instead of intact hCG).

What is the accuracy?

• 50% of twins can be predicted

• 80% to 90% Down Syndrome predicted in women over 36 years old

• 60% to 70% Down Syndrome predicted in women under 36 years old

• 85 % of open neural tube defects

• 75% ventral wall defects

Introduction

1. The Triple Test - Overview

2. The Triple Test - Detail and Results

3. Amniocentesis

4. CVS