Down syndrome affects 1 in every 500 live births in South Africa (March of Dimes 2008). That’s just a fraction of total cases, as early detection methods now allow parents to abort pregnancies when faced with a high risk of having a child with Down syndrome. The condition becomes increasingly common for older mothers, particularly those above the age of 35.

Finding Down syndrome in a fetus is a two-step process, involving first a screening for risk and then a diagnostic test to determine if the defect truly exists.

Screening Methods

Doctors have a number of ways to identify high-risk pregnancies.

They measure the mother’s blood levels of certain proteins and hormones.

And they use ultrasound to scan so-called nuchal translucency – the thickness of a layer of fluid that forms near the neck of a developing fetus. Too much liquid there is often a sign of Down syndrome.

Diagnostic Tests – Two procedures can definitely detect Down syndrome

1. Amniocentesis

A test performed after the 12th week of pregnancy looks at the cells in the fluid that surrounds the fetus. This procedure holds about a half percent increased risk of miscarriage.

2. Chorionic-villus sampling (CVS)

During this test placental cells are analyzed for the chromosome abnormality and can be done as early as 10 and a half weeks of pregnancy. This procedure increases the risk of a miscarriage by about 1 percent.

3. Nuchal Tranlucency test.

This is an ultrasound that can be done on the pregnant mother during which the space at the back on the neck of the baby (fetus) is checked for more fluid. This can be done from between 11 and 14 weeks of pregnancy and the detection rate of this test is 80%

The ‘Holy Grail’ for Down syndrome is a non-invasive diagnostic test that doesn’t threaten the fetus. Researchers are working on ways to locate and screen the few fetal cells that float through the mother’s blood stream. These cells are so rare, however, that finding them efficiently has so far been impractical.

What researchers suggest

In the latest report, researchers in London propose that combining results from first and second trimester tests might be a more accurate way to identify fetuses at high risk for Down syndrome. Doing so, they argue would reduce the number of invasive tests preformed and therefore trim the risk of miscarriage for healthy fetuses.

The researchers lumped together results from previous studies of various screening tests for signs of Down syndrome given in the first three months of pregnancy and those used in the second trimester. Methods included protein levels and ultrasound readings of nuchal translucency in the first third and a trio of blood tests taken in the second trimester.

The combined approach had a detection rate of 85 percent for high-risk Down syndrome pregnancies, with less than one false-positive per 100 tests, the researchers report. That’s between 5 percent and 22 percent more accurate than standard techniques, they add, based on known false-positive rates.

If the integrated system were used instead of acting on first trimester screening results, the researchers say, the number of unnecessary invasive diagnostic tests would drop by 80 percent, thus saving many fetuses not affected by Down syndrome.

We (DSSA) strongly urge expecting parents to research and access correct information regarding Down syndrome. One way of doing so is by contacting the nearest branch to you in order to be put into contact with one of our trained “New Parent Counsellor”
 

STATEMENT OF DOWN SYNDROME SOUTH AFRICA ON PRE NATAL TESTING AND TERMINATION

Down Syndrome South Africa does not consider Down syndrome a reason for termination. People with Down syndrome can lead and do lead full and rewarding lives and make a valuable contribution to our society. However we realize that parents need to make the right decision for themselves.

The organisation accepts that prenatal testing for Down syndrome is becoming a routine part of antenatal care. Any diagnostic test, which can give a definite result early in pregnancy, without the risk of miscarriage, is considered to be more desirable than those presenting a risk.

We strongly believe that any programme of testing for a generic condition must be accompanied by non-directive counselling. Individuals can then make a decision based on full and accurate information. Appropriate support must be provided regardless of the choices made.