Everything You Need to Know About Triple Test Screening

During pregnancy, it is advisable to get checked for birth defects because they could harm the baby. A number of these tests are done, among them is the triple screening test – also simply known as the triple test or triple screen. It may also be referred to as Bart’s test or the Kettering test.

Why is triple screening test done?The triple screen test is mostly done to screen for Down syndrome. Although, it can also detect the presence of genes that may lead to other genetic disorders.

Some of these include:
• Edward’s syndrome
• Turner syndrome
• Open neural tube defects like spina bifida and anencephaly
• Steroid sulfatase deficiency
• Fetal death, etc.

It is important to remember that the test is not done to diagnose the presence of these conditions but rather to detect whether the baby may be at risk of being born with one of the disorders mentioned above.

In cases when the tests show abnormal results, further tests known as diagnostic tests are done in order to confirm if the fetus truly has the chromosomal defect or not. As such, you should not take the results of the triple screen test as a diagnosis. Rather the results of this test should be considered as screening results.

How is the triple test screening performed?The triple screening test should be performed during the second trimester – long enough into the baby’s maturity that the organs have begun developing but still early enough to implement any treatment necessary.

The recommended time for the test is between the 16th and 18th weeks of pregnancy. But it can still be effective between the 15th and 22nd week.

A blood sample is taken from the mother, which just takes about 5 minutes, after which the sample is taken to the laboratory for testing. The results should be complete within a few days.

As its name suggests, this test checks for the serum levels of 3 components which are important substances in the placenta:

• Alpha-fetoprotein (AFP) – a protein produced by the fetus. If the levels of AFP are higher than normally, it signifies potential birth defects such as neural tube defects, failure of the abdomen of the fetus to close, etc.

• Human chorionic gonadotropin (hCG) – a hormone produced by the placenta, and if the levels of this hormone are lower than they should base on the gestational age of the fetus, it signifies a problem with the pregnancy, a possibility for a miscarriage or even an ectopic pregnancy. On the other hands, if the levels of hCG are much higher than they normally should, this can signify a molar pregnancy, multiple pregnancies, etc.

• Estriol – is an estrogen hormone produced by both the fetus and placenta. If the levels of estriol are lower than they should, there is a great chance of having a baby with a chromosomal disorder. This is especially true when this result is combined with abnormal results of hCG and AFP levels.

However, it is possible to get a false result from the triple screen test. This is most often due to the inaccurate dating of the pregnancy.

The triple screen test has a 5% false positive rate and 70% sensitivity to the genetic markets. A more accurate test is the quad test which has an added component and is 81% sensitive with only a 5% false positive rate.

What to do after the triple screen test?
If the test shows an abnormal result, diagnostic tests such as amniocentesis and chorionic villus sampling are carried out. These are more accurate tests with a higher sensitivity.

However, these diagnostic tests have an increased risk for complications including injuries to the fetus and miscarriage.

Who should get tested?
In many countries, triple screening test belongs to routine tests and examinations performed such as a sonogram in every pregnancy.

This screening test is especially recommended in cases when:
• The woman is over 35 years old,
• There is a family history of birth defects,
• The woman has used drugs and other harmful medications during the pregnancy,
• The woman has been exposed to high levels of radiation during the pregnancy,
• The woman had a viral infection during the pregnancy,
• The woman has diabetes and even takes insulin as a treatment for her condition, etc.