Overview
The “double marker test” is a screening blood test used during early pregnancy to assess the risk of specific chromosomal abnormalities in the developing foetus. It assesses key biochemical markers in the mother’s blood and is typically combined with ultrasound findings (such as NT scan). The test is not diagnostic; it just gives a risk assessment, not a definitive answer.
In this article, we will explain what the test is, when and why it is offered, what the results mean, how accurate it is, etc., to help you understand in a simple manner.
What is the Double Marker Test?
The Double Marker Test is a prenatal blood screening test performed during the first trimester of pregnancy. It measures two biochemical markers in the mother’s blood: free beta-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A).
When combined with maternal age, gestational age, and sometimes an ultrasound (such as a Nuchal Translucency or NT scan), the test provides an estimate of whether the baby may have certain chromosomal conditions, including Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), or Patau syndrome (trisomy 13).
When is the Double Marker Test Done?
Doctors usually prescribe the double marker test between the 10th and 14th weeks of pregnancy. Some may even recommend it anytime from 9 to 13 weeks of the pregnancy. It is usually the time when the nuchal translucency (NT) scan is also prescribed.
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Why is Double Marker Test Done?
- The double marker test is done to provide early information about the risk of chromosomal abnormalities in the unborn baby.
- Helps in making informed decisions: whether to carry out further diagnostic tests, prepare emotionally/medically for specific outcomes, or reassure if the risk is low.
- It is particularly recommended for higher-risk pregnancies (for example, maternal age over 35, previous child with chromosomal condition, family history, abnormal ultrasound findings), though many clinicians offer it to all pregnant women as part of routine screening.
Double Marker Test Procedure
- A blood sample is drawn from the expectant mother. It is simple, non-invasive and poses no risk to the baby.
- The lab measures levels of free β-hCG and PAPP-A.
- These marker levels are combined with other factors (maternal age, gestational age, and ultrasound measurements) to calculate a risk figure (for example, “1 in 250”).
- Minimal preparation: Typically, fasting is not required. The main thing is accurate dating of pregnancy and a reliable ultrasound.
Interpreting Double Marker Test Results
If you’ve received your double marker test report, do not try to interpret it yourself, as it may cause unnecessary confusion. Doctors will interpret it in the context of the bigger picture.
| Marker/Factor | What is Measured | Typical Interpretation |
|---|---|---|
| Free β-hCG | Hormone produced by the placenta (free form) | Higher or lower than expected may raise risk |
| PAPP-A | Protein produced by the placenta/fetus | Lower than expected may raise risk |
| Maternal age / gestational age/ultrasound (NT) | Non-biochemical factors | Older age, increased NT thickness → higher risk |
| Risk ratio (e.g., 1:250) | Estimate of the probability of chromosomal condition | Lower denominator = higher risk |
Note: Exact “normal” ranges vary by laboratory and population.
What the Results Mean in Plain Terms?
- Low-risk / “screen negative” : The risk estimate is low, indicating that the chances of the baby having the tested chromosomal abnormalities are minimal. This is reassuring, but does not guarantee the baby has no condition.
- High-risk / “screen positive” : The risk estimate is elevated—meaning your baby may have one of the tested conditions. It does not confirm the condition, but your doctor may recommend further diagnostic testing.
It is essential to view results in the context of your doctor's assessment, taking into account factors such as maternal age, ultrasound findings, health status, and lab values.
Benefits of Double Marker Test
- Non-invasive : The test is safe and requires a simple blood draw. Hence, there is no risk to the mother or the baby
- Early in pregnancy : It allows time for planning, decision-making, and emotional preparation.
- Cost-effective : Compared to more invasive diagnostic procedures.
Limitations of Double Marker Test in Pregnancy
- Not definitive : The test may indicate a risk, but does not provide a definitive diagnosis. Based on the identified risk factor, the doctors will need to continuously monitor the patient and perform further testing.
- Potential for false positives and false negatives : The test can sometimes assign a low risk rating to a baby who may have an abnormality, and vice versa, indicating a high risk to a baby who may turn out completely normal.
- The accuracy of the test in determining the results depends on factors such as gestational age and maternal characteristics.
- The double marker test is not available for all types of genetic or structural anomalies. It only screens for certain chromosomal conditions (trisomies 21, 18, 13).
Important Considerations
- This test is optional (though often recommended): you and your healthcare provider should discuss whether it is right for you.
- If you receive a high-risk result, that does not mean you must end the pregnancy; it means further evaluation is appropriate.
- Emotional support and counselling are essential: a high-risk result can provoke anxiety.
- In places like India, costs and availability vary; some labs offer home collection, packages, etc.
Who Should Consider the Double Marker Test
- Pregnant women in the first trimester (between ~10 and 14 weeks) who want early screening.
- Women with higher baseline risk (e.g., age over 35, family history of chromosomal conditions, previous affected pregnancy).
- Women who prefer to know early to help prepare for further testing, decisions, and emotional readiness.
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Who Should Not Consider the Double Marker Test
- If their healthcare provider advises that it is not necessary in their particular scenario (e.g., very low risk or other screening options are already in place).
- If they prefer to wait for later screening or diagnostic tests.
- If they do not wish to know risk information or prefer to avoid screening, they should discuss the decision with their provider.
Conclusion
The double marker test is an early step that helps parents and doctors better understand a baby’s health. It doesn’t confirm or deny any condition, but it provides a clearer picture of possible risks, such as Down, Edwards, or Patau syndromes. It is nothing to be scared of. Think of it as a guide: one that helps you and your doctor make informed choices and plan with confidence and care.
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Frequently Asked Questions
Is the double marker test the same as the NT scan?
No, the NT (Nuchal translucency) scan is an ultrasound measurement of fluid at the back of the baby’s neck. The double marker test is a blood test measuring biochemical markers. Often they are done together for first-trimester screening.
Do I need to fast or prepare in any special way for the blood draw?
Not really. It is a simple blood test that requires no special preparation. Consult your doctor before undergoing the tests.
Will insurance cover the cost of double marker tests?
Coverage varies depending on the region, health insurance, and medical guidelines. In some places, it may be part of routine prenatal screening; in others, you may need to ask your healthcare provider or insurance company.
If the result is “high risk,” what next?
Your doctor will usually recommend further testing (such as non-invasive prenatal testing (NIPT), Chorionic Villus Sampling (CVS), or Amniocentesis) to obtain more definitive information. Counselling is important as well.
Can I do the Double Marker Test without an ultrasound?
It’s possible, but combining it with the NT (Nuchal Translucency) scan gives a more accurate risk assessment. Most doctors recommend performing both tests together to obtain results that provide a clearer picture.