Double Marker Test – Procedure, Normal Range, Benefits and Risks

Overview

Pregnancy is a blissful phase in a woman’s life. It may also be filled with concerns about the health of an unborn child. Several tests and scans can be performed to put the mind of the expecting parents at ease. One such test is the pregnancy double marker test. Read on to know more about the double marker test, associated benefits, and the reasons why it may be prescribed.

What is a pregnancy double marker test?

As a part of comprehensive antenatal screening, a double marker test or maternal serum screening can be used to determine the possibilities of complications with the unborn child.   

When is the pregnancy double marker test required?

This test is usually prescribed during the first trimester to avoid unforeseen complications after childbirth. The screening involves checking blood levels of both beta-human chorionic gonadotropin (free beta – hCG) and pregnancy-related protein like A (PAPP-A).

The window to undergo this screening is usually relatively small. The healthcare provider may be able to help decide a suitable time. Generally, the procedure is performed sometime between the gestational age of 11 and 14 weeks.

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What is the procedure for double marker test screening?

The double marker test is not mandatory. However, it is recommended if the expecting mother is over the age of 35 or if she has an elevated risk of chromosomal issues.

The blood test is interpreted along with an ultrasound test known as nuchal translucency (NT) scan that examines clear tissue at the back of the neck of your baby. The test focuses on two markers, Free Beta hCG (human chorionic gonadotrophin) and PAPP – A (pregnancy-associated plasma protein-A).

The placenta produces a hormone called Free Beta hCG. It is a glycoprotein hormone. High levels of Free Beta hCG may indicate a higher risk of Trisomy 18 and Down syndrome.

On the other hand, PAAP-A is a vital plasma protein. Low levels of this protein can indicate an elevated risk of Down syndrome.

A trisomy is a chromosomal condition characterised by an additional chromosome, such as:

• Down syndrome: A common trisomy, down syndrome is also referred to as trisomy 21 as there is an extra copy of chromosome 21.
• Trisomy 18 and trisomy 13: These are common chromosomal abnormalities that involve an extra copy of chromosome 13 (Patau’s syndrome) or chromosome 18 (Edward’s syndrome) 

Levels of hCG and PAPP-A may be either lower or higher than ‘normal’ in pregnancies with these chromosomal abnormalities.

What is the normal range for hCG and PAAP – A?

You will receive a low, moderate, or high-risk result. Low-risk (screen-negative) is called a “normal” result and means that there is a low probability of the baby having chromosomal abnormalities.

When do you need medical help?

If the test results are inconclusive or indicate abnormalities, it is best advised to visit the doctor immediately.

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What are the benefits of the procedure?

 This procedure can help detect

• Down syndrome
• Trisomy 18 which results in mental retardation and severe birth defects
• Trisomy 21 which causes mental disorders, heart issues, and other health conditions affecting vital organs among newborn children.

What are the risks associated with double marker test screening?

As this is a non-invasive blood test, there are no risks associated with the double marker test. It is a routine test. But one should be sure to follow the doctor’s instructions and immediately contact the healthcare provider if there are any concerns regarding the tests or pregnancy.

How should a person prepare for the double marker test ?

It is a simple test similar to a blood test. The patient can continue to eat and drink as usual unless advised otherwise. There are no risks linked to the test as it is a non-invasive procedure.

What can the results of the double test marker indicate?

The pregnant woman will receive the result as low-, moderate-, or high-risk.  

If an expectant mother receives a low-risk or screen-negative result, it means that the baby has a low probability of having chromosomal abnormalities.

However, if the results are in the normal range and there are other indicators such as family history, maternal age, and other specific risk factors, then the doctor may recommend further testing and screening.

Keep in mind a low-risk result doesn’t always imply that the unborn child will be born without any chromosomal defects. It is important to understand that this test only looks for indicators for Down Syndrome, Trisomy 13, and Trisomy 18. It does not indicate any other conditions.

What is the difference between a double marker test and an NT scan?

NT scan is an ultrasound and a double marker test is a blood test. The doctor recommends both these tests during the first trimester to get accurate results for any possibilities of chromosomal abnormalities. The information from both tests can give a result of low-, moderate or high risk for abnormalities. The NT scan is less effective when it’s not performed with the double test marker.

Conclusion

During pregnancy, getting to know the health of the baby is important for all soon-to-be-parents. This is why several tests such as the double test marker are recommended by doctors. These are only indicators for future chromosomal abnormalities and may not be definitive. It is up to the parents to decide if they want to take the test or not.

Frequently Asked Questions

Is the test painful?

As this is a blood test, the pain is minimal to nil. The only pain a person may experience is the prick of the needle when drawing the blood.

What are the chromosomal abnormalities found in this test?

The following possible chromosomal abnormalities may be identified through this test:

• Down syndrome
• Trisomy 18
• Trisomy 13

Is the double test marker mandatory?

This test is not mandatory. But it is recommended to find out if there are any possibilities or risks of chromosomal abnormalities.