Double Marker Test – Why is it necessary?

double marker test

First of all congratulations. You are pregnant and soon a new life will accompany you. But the 9 months of pregnancy journey is not easy. Expecting mother is showered with well being and dietary advice. Of course you need to shift to a healthy diet and lifestyle and routine checkup is must for pregnant females. To ensure the health of your growing baby and avoid problems in future certain tests are recommended by the doctor. One such test is the double marker test.

What Is Double Marker Test?

A double market test is a blood test done to rule out anomalies in the chromosomal development of the baby growing in the mother’s womb. It is also known as maternal serum screening.

This test plays important role in detecting neurological issues in foetus such as Edward syndrome or Down syndrome that affects the growth of the baby in the womb or later in life. This test screens for the level of pregnancy-associated plasm protein A and beta-human chorionic gonadotrophin in the blood.

In pregnancies with chromosomal abnormalities the level of hCG or PAPP-A is either lower or higher than the normal.

However this test is a predictive test and not a definitive test. Its result tells us the chance of chromosomal abnormality. Also, the blood test is done along with nuchal translucency scan with is an ultrasound that examines clear tissue at the back of fetus neck.

A double marker test is not mandatory. Mostly pregnant females above 35 years of age, with history of insulin dependant type 1 diabetes or with family history of birth abnormalities are recommended to get this test.

What Is The Need Of Double Marker Test?

The double marker test detects accurately any abnormalities present in the growing baby. The test assesses if the developing baby is at risk of any mental disorder. Primarily the test is done to detect Down syndrome and also helps to detect Trisomy 18 that causes severe birth defects and mental retardation and Trisomy 21.T that causes heart disorders, mental disorders and other health conditions that affects vital organs of the body.  

A typical pregnancy has 22 pairs of XX chromosomes if its a female fetuses or 22 pair of XY chromosome in male fetuses. When there is extra chromosomes the condition is known as trisomy such as:

Down Syndrome – It is common trisomy. It is also referred to as trisomy 21 as there is an extra copy of chromosome 21.

Trisomy 18 and trisomy 13 – Trisomy 18 involves extra copy of chromosome 18 and trisomy 13 involves extra copy of chromosome 13

If the test gives a positive result, further diagnosis is done to pinpoint the problem. Advance tests are done to rule out Down’s syndrome. If the positive test detects a neurological disorder in unborn babies, parents can choose to terminate the pregnancy at an early stage.

How Is Double Marker Test Done?

Double market test is a blood test combined with an ultrasound. A blood sample is taken to check two major elements a protein and a hormone. The glycoprotein hormone is Free Beta Human Chorionic gonadotrophin developed by the placenta during pregnancy. The protein is Pregnancy-associated plasma protein A that is also an essential protein for pregnant women.

If beta hCG is high  in pregnant women it indicates high risk of Down’s syndrome and Trisomy 18. On the other hand a low level of ‘pregnancy associated plasma protein A’ indicates high risk  of Down’s syndrome.

The Timing of Double Marker Test

In general, there is relative a slim time window to perform double marker test. Your gynaecologist or the healthcare provider will make an appointment somewhere near the end of first trimester or early second trimester. To be specific the blood is drawn sometime between 11 to 14 week of conception.

What Is The Normal Value Of Double Marker Test?

The normal value of Double Marker test for hCG in pregnant women of all age groups is 25700-288000 mIU/ml. The normal value of Double marker test for PAPP-A is 1 MoM for females of all age groups.

Interpretation Of The Test Result

Along with the blood test result, the age of the fetus observed during ultrasound and mother’s age is also taken into account for result interpretation as all these factors affect the development. The result may be screen positive or screen negative. The result is presented as a ratio. The ratio of 1:1000  and above is termed screen negative and the ratio between 1:10 to 1:250 is termed as screen positive. Mothers above 35 years of age is at high risk that their baby will develop the neurological disorder.

The ratio helps to understand the possibility of a child suffering from any congenital disorder. The ratio depicts the chances of the child to have disorder over a number of pregnancies. So if the ratio is 1:1000; means only 1 child out of 1000 pregnancies may suffer from congenital disorder and this ratio is almost negligible.

How To Prepare Yourself For The Double Marker Test

No preparation is needed for the double marker test. However, if you are on certain medications during your pregnancy, your doctor will let you know if you need to stop the medications until the test is performed.

However, before deciding to go for a double marker test we suggest you to analyse what the test result means to you in a long run.

Ask yourself following questions:

  • Will knowing about possible abnormality worsen or ease your anxiety.
  • Will the test result change the way you are managing pregnancy
  • If the test result predicts heightened risk, will you go for invasive testing?

Going for a double marker test is your personal choice and depends on your health history. It is better to discuss your thought with your gynaecologist before taking any decision.

What Should You Expect When the Test Is Done?

Double Marker test is a simple a blood test and not a non-fasting test. Eat and drink normally before your appointment unless you are instructed by your doctor to do otherwise.

The turnaround time varies according to labs. In general result is received in about 3-7 days.

If in case the result comes to moderate or high-risk better consult with a genetic counselor to know more.

Any disadvantage of Double Marker Test

  • The accuracy of the result of double marker test depends on the equipment used and the doctor’s skill.
  • A low-risk result not always mean that the baby will not have any issue.
  • Double marker test only looks at markers for Down syndrome, trisomy 18 and trisomy 13 and not other abnormalities.
  • This test is little costly and may not be feasible for all. The test may not available in every city due to the high cost and types of equipment required.

Cost Of Double Marker Test

The cost of double marker test may vary across hospitals, across cities and across countries depending on availability of the test, experience of doctors and quality.

We suggest you to call your insurance provider to know if the double marker test is covered or whether you need pre-authorisation. If you do not have, insurance better call the lab or hospital to find out the cost as well as the potential payment plan. Keep in mind that this test is mostly done in conjugation with nuchal translucency scan so you need to pay for both the tests for complete screening.

Every expecting parent wants to ensure that their baby develops healthy and is capable of leading a healthy life. The decision of terminating a pregnancy if the double marker test is positive is a parent’s choice. The focus is to ensure the best outcome.