Prenatal Screening Tests – What Are the Double and Triple Tests?

Pregnant women are often referred by their gynecologist to undergo the Double or Triple test, depending on the stage of pregnancy. Both tests are non-invasive screening tests. The term “screening” means “checking”. These are combined tests, meaning the results are a combination of specific parameters obtained from an ultrasound examination by the gynecologist and values obtained from a blood analysis of the mother.

Why Are These Tests Performed?

The Double/Triple test is a blood test conducted during pregnancy to identify pregnancies with the most common birth defects. It also aims to reduce the number of pregnant women referred for amniocentesis and other invasive procedures. This type of combined screening is non-invasive and financially accessible to everyone.

When and how is the Double Test or Triple Test Performed?

Whether a pregnant woman will be referred for a Double or Triple test depends on the stage of pregnancy.
1. Double Test (Dabl Test) The Double test is a screening test performed in the first trimester, between the 11th and 14th weeks of gestation. Pregnant women are most commonly referred for this test at around the 12th week of pregnancy. The test measures two biomarkers from the mother’s blood:

• Free Beta hCG (free human chorionic gonadotropin)
• PAPP-A (Pregnancy-associated plasma protein A)

This test assesses the likelihood of the most common chromosomal abnormalities:

• Trisomy 21 (Down syndrome),
• Trisomy 18 (Edwards syndrome),
• Trisomy 13 (Patau syndrome)

However, this test cannot evaluate the likelihood of neural tube defects, which affect brain and spinal cord development.

2. Triple Test The Triple test is a screening test conducted between the 15th and 20th weeks of gestation. The name “Triple” indicates that three biomarkers are measured:

• AFP (Alpha-fetoprotein) – derived from the fetus
• FE3 (Free Estriol) – unconjugated estriol, derived from the fetus and placenta
• Free Beta hCG – human chorionic gonadotropin, produced by the placenta

This test estimates the likelihood of:

• Neural tube defects (disorders in brain and spinal cord development)
• Chromosomal abnormalities (Down syndrome, Edwards syndrome, Patau syndrome, etc.)

It is important to note that, as this is a combined test, the ultrasound report from the gynecologist should not be older than 48 hours. Ideally, the ultrasound and blood sample collection for the required biomarkers should be performed on the same day if possible. The laboratory, processes the data by using the relevant fetal measurements and information from the ultrasound report. Personal medical history data of the mother (such as age, smoking status, body weight, whether the pregnancy is natural or IVF, presence of diabetes) is also considered. All this information is entered into licensed software (PRISCA) that generates the test results based on the entered values.
No special preparation is required for the blood draw, but it is advisable not to collect the sample immediately after a meal. The analysis is performed routinely, and results are available within the same day.