Triple screen test in pregnancy

Also known as triple screen, multiple marker screen, and AFP triple screen, is a maternal blood screening test that looks for three specific substances: AFP, hCG, and estriol.

AFP: alpha-fetoprotein is a protein that is produced by the fetus.
HCG: Human chorionic gonadotropin is a hormone produced by the placenta.
Estriol: Estriol is an estrogen produced by both the fetus and the placenta.

It is a non-invasive procedure performed through a blood test with little or no known risk to the mother or developing baby.

What is a screening test?

It is very important to remember what a screening test is before you do it. This will help reduce the anxiety that may accompany the test results. Screening tests are not limited to blood test results. They compare a number of different factors (including age, ethnicity, blood test results) and then evaluate a person's chances of having an anomaly.

These tests do NOT diagnose the problem; they only signal that further testing is needed.

How is the triple test done?

The triple screening test involves drawing blood from the mother, which takes about 5-10 minutes. The blood sample is then sent to a laboratory for analysis. The results usually take a few days.

What are the risks and side effects for the mother or baby?

Other than the discomfort of drawing blood, there are no known risks or side effects associated with the triple screening test.

When is the triple test done?

A triple screening test is performed between the 15th and 20th weeks of pregnancy, although results obtained between the 16th and 18th weeks are most accurate.

All pregnant women should be offered triple screening, but it is recommended for women who:

Have a family history of birth defects
Are 35 years or older
Used possible harmful medications or drugs during pregnancy
Have diabetes and use insulin
Had a viral infection during pregnancy
Have been exposed to high levels of radiation

What is the triple screen test looking for?

The triple screen measures high and low levels of AFP and abnormal levels of hCG and estriol. The results are combined with maternal age, weight, ethnicity, and pregnancy to assess the likelihood of potential genetic disorders.

High levels of AFP may indicate that the developing child has a neural tube defect such as spina bifida or anencephaly.

However, the most common cause of high AFP levels is inaccurate dating of pregnancy. Low AFP levels and abnormal levels of hCG and estriol may indicate that the developing baby has trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), or another type of chromosomal abnormality.

Although the main reason for testing is to identify genetic disorders, the results of triple screening can also be used to detect:

Multiple pregnancy
Pregnancies that are more or less advanced than thought

What do the results of the triple test mean?

It is important to remember that the triple test is screening and not diagnostic. This test only notes that the mother has a possible risk of carrying a child with a genetic disease. Triple screening is known to have a high false positive rate.

Abnormal test results require further testing to establish a diagnosis.

A more conservative approach is to perform a second triple screen followed by high-definition ultrasound. If the test continues to show abnormal results, a more invasive procedure, such as an amniocentesis, may be performed. Invasive testing procedures should be carefully discussed with your doctor and between you and your partner.

Additional advice and discussions with a counselor, social worker, or minister may be helpful.

What are the reasons for additional testing?

Triple screening is a routine screening that is not invasive and does not pose any risk to the mother or baby. Abnormal triple screen results often require additional testing. The reasons why further testing should be done vary from person to person and couple to couple.

Performing additional tests allows you to confirm the diagnosis, and then opens up certain possibilities for you:

Pursue potential interventions that may exist (fetal surgery for spina bifida)
Begin planning for a child with special needs
Start addressing anticipated lifestyle changes
Identify support groups and resources
Make a decision about carrying the child to term

Some individuals or couples may refuse to be tested or additional tested for a number of reasons:

They are satisfied with the results, regardless of the outcome
For personal, moral or religious reasons, deciding to carry a child to term is not an option.
Some parents choose not to allow tests that could harm a developing child.

It is important to carefully discuss the risks and benefits of testing with your doctor. Your doctor will help you evaluate whether the benefits of the results may outweigh the risks of the procedure.