Double test – blood tests during the first trimester of pregnancy

Proven content

In the last dozen or so years, tremendous advances in medicine have made the fetus treated like any other patient who can be examined and even treated in the womb. Correct and early diagnosis is of great importance for the continuation of pregnancy and for the management immediately after childbirth. One of the important prenatal tests is the double test.

What is a double test?

The duplicate test is a biochemical test carried out in a pregnant woman before the baby is born. It belongs to the group of non-invasive prenatal tests because it only involves taking blood from the expectant mother. It does not require administration of any pharmacological agents or interference in the organism of the fetus. The blood sample is tested for levels of fetal AFP protein and free beta-HCG subunit. Based on the results, the likelihood of birth defects in the fetus is assessed.

Why is it worth doing a double test?

By performing a double test, it is possible to detect Down’s syndrome, Edwards’ syndrome and other most common chromosomal aberrations (genetic defects) in the fetus. Abnormal levels of AFP may also indicate spina bifida or anencephaly. Double test sensitivity is estimated at around 60 percent. This test is non-invasive and therefore completely safe – both for the mother and the fetus.

In most countries, complete prenatal diagnosis (including a dual test) is performed in women over 35 years of age, as this age group has a higher risk of having a baby with Down’s syndrome and other chromosomal abnormalities. Only every fifth child with these defects gives birth to life. Unfortunately, as much as 35-70 percent. children with Down syndrome are the offspring of mothers under 80 years of age. This is why proper screening is so important in pregnant women.

Also read about others non-invasive prenatal testingwhich include:

1. SANCO test;
2. test Harmony.

What is the test?

The double test is based on the determination of the level of two proteins in the blood: AFP and the free beta-HCG subunit (chorionic gonadotropin). It is made in between 11 a 13. (+6 days) week of pregnancy. The doctor interprets the results, referring to the results of other tests, including pregnancy ultrasound.

Who should do a double test?

Although the double test can be performed by pregnant women of any age, it is not a mandatory test! If you are under the age of 35, it may be performed to determine the risk of your baby developing birth defects. If you become a mother after your 35th birthday and you are concerned about invasive prenatal tests (e.g. amniocentesis) ordered by your doctor, you can only opt for non-invasive tests (including a double test), which will approximate the risk of your baby developing the defect congenital.

Recommendations for prenatal diagnosis for birth defects apply to women:

1. who will be older than 35 at the time of the birth of the child,
2. in whom the ultrasound examination of the fetus has features suggesting the presence of a congenital defect,
3. who had an abnormal biochemical test result,
4. who have had birth defects with the fetus in previous pregnancies,
5. who (or their partners) have chromosomal abnormalities,
6. who are at a higher risk of having a child with a congenital defect (in the early stages of pregnancy, they used antiepileptic drugs, antibiotics – tetracyclines, were given chemotherapy, radiation).

The dual test is performed in the first trimester of pregnancy, similar to the PAPP-A test. It is recommended at a later stage of fetal development (14–20 weeks) triple screening test.

Is the examination payable?

Double test free of charge can be performed by pregnant women who are referred by the doctor receiving the NHF for examination due to one of the above-mentioned indications. If there are no disturbing reasons and we are not sent for the examination, but we are concerned about the child’s health, we can also do it for a fee.

For more information:

1. Indications for prenatal tests. Price and refund
2. Prenatal tests – is it worth doing and when?

How to prepare for the test?

The test does not require any special preparation. It does not matter at what time the blood is drawn or whether you have eaten a meal before. As with any blood test, it is a good idea to drink a glass of water half an hour before the blood sample is collected. Please note that the result should be assessed by a doctor. He will need additional information in the form of a medical history and other diagnostic test results.

How to interpret the results?

Double test does not detect 100 percent cases of Down’s syndrome or other fetal pathologies. The test result is determined taking into account the risk resulting from the mother’s age. Thus, if a woman is 30 years old, the age-related risk of developing a defect in her fetus is approximately 1: 400. If the risk of a double test in the same woman is around 1: 10000, then the probability of a birth defect in the baby is much lower than it would appear from the mother’s age. This is very good news for future parents.

Positive (invalid) result of the test it is not synonymous with fetal disease. It only means that he is at increased risk of Down syndrome and Edwards syndrome. In this case, your doctor may order further tests to confirm this risk. The higher its value, the greater the probability that the child will be born sick. Remember, however, that most high-risk women give birth to healthy babies. It does not change the fact that in pregnant women after the age of 35 the probability of an incorrect double test result is higher than in younger women.

Negative (correct) result means that the risk of developing Down’s syndrome and Edwards’ syndrome in the fetus is low. Further testing is not recommended then. Remember, however, that the correct double test result does not give 100%. a guarantee that the baby will be born healthy.

Invasive prenatal testing

If the results of a screening test, such as the duplicate test, are abnormal, you may need to undergo an invasive procedure. It will enable the diagnosis of a fetal defect with a probability of up to 99%. Most often, amniocentesis, chorionic villus sampling or cordocentesis is performed. All the above-mentioned methods are associated with a minimal risk of complications (from 1 to 3%), therefore they are performed only with specific indications. Side effects include bleeding, intrauterine infections, premature births and miscarriages.

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