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Screening for Down Syndrome and Other Fetal Defects

1 January 2025

Screening to detect Down syndrome involves a series of blood tests and ultrasounds that are performed based on the stages of pregnancy and are calculated in combination with the mother's age and the week of pregnancy, and ultimately, with the help of special computer software, a calculation is made that determines the level of statistical risk of delivering a newborn with the syndrome.

Blood tests

  • Early screening (First Trimester Screening): Performed from Week 11 until the end of Week 13 of pregnancy, it measures the level of two indicators—the protein PAPP-A and the hormone HCG—in the mother’s blood. The results of the blood tests are combined with the results of the nuchal translucency.
  • Triple Test (Second Trimester Screening): Performed between Week 16 and the end of Week 20 of pregnancy and tests the values of 6 indicators in the mother’s blood: the fetal protein (AFP), the placental hormone (HCG), and the estriol hormone (Estriol-E3).
  • NIPT/NIP Test: Test of the fetal DNA that is found in minute quantities in the mother’s blood. 

Ultrasound

  • Nuchal translucency: performed between Week 11 and until the end of Week 13 of pregnancy. In this test, an ultrasound is performed to measure the thickness of the fluid behind the fetus’s neck as well as fetal length from head to the end of the spine. The test also detects fetal defects (primarily heart defects). The data obtained is used to assess the risk of Down syndrome or other fetal conditions.
  • Early screening: An ultrasound of the fetal organs and measurement of the fetus (such as circumference of the head, abdomen, etc.) designed to detect structural changes or defects in the early stages of pregnancy. The screening is performed between Week 14 and until the end of Week 16 of pregnancy. It can help detect suspicious findings that may indicate the presence of genetic syndromes, such as Down syndrome. If such a suspicion arises, the woman may be referred to genetic counseling and other diagnostic tests.
  • Later anatomical screening: an ultrasound of the fetal organs and measurement of the fetus (such as circumference of the head, abdomen, etc.) designed to detect structural changes or defects in the early stages of pregnancy. The test was not designed to determine the level of risk of Down syndrome, but in certain cases, the risk may be assessed based on abnormal findings or structural indications that arose during the test (in combination with the weighted screening).

Down syndrome (Trisomy 21) is largely attributed to abnormal chromosome division that largely occurs even before the sperm meets the egg (fertilization). Today, it is still not possible to prevent this abnormal division so that, essentially, every woman, of any age, can give birth to a newborn with Down syndrome. The level of risk primarily depends on the mother’s age and is higher the older the mother is. There are extremely rare family situations in which the risk of Down syndrome is particularly high due to a chromosomal translocation in one of the parents. Taking certain medications during pregnancy can also increase the risk of chromosomal anomalies.

There are currently a range of screening tests to detect pregnancies at high risk of delivering a fetus with Down syndrome. 

Screening to detect Down syndrome involves a series of blood tests and ultrasounds that are performed based on the stages of pregnancy and are calculated in combination with the mother's age and the week of pregnancy, and ultimately, with the help of special computer software, a calculation is made that determines the level of risk of delivering a newborn with the syndrome. These tests are statistical and not 100% reliable.

To make the process easier and to put things in order for you, attached below is a list of all the screening tests available to detect Down syndrome, what their purpose is, when each of them must be performed, and whether it involves a fee. It remains for you to decide which tests you would like to perform and find out with your HMO where you can perform the test depending on where you live. 

Blood tests

Early tests (First Trimester Screening)

  • What is being tested: The test measures the level of 2 indicators, PAPP-A and HCG, in the mother’s blood. The results of the blood test are weighted with the results of the nuchal translucency (see below), and hence the recommendation to perform them around the date of the nuchal translucency. 
  • When the test is performed: Between Week 11 and until the end of Week 13 of pregnancy. 
  • Purpose of the test: To identify fetuses at increased risk of Down syndrome.
  • Eligibility: The test is included in the health services basket and is performed in all HMO laboratories with a medical referral, with a partial deductible. 

Triple Test (AFP, Triple Test)

  • What is being tested: Test of values of 3 indicators in the mother’s blood: the fetal protein (AFP), the placental hormone (HCG), and the estriol hormone (Estriol-E3).
  • When the test is performed: Between Week 16 and until the end of Week 20 of pregnancy.
  • Purpose of the test: To identify fetuses at increased risk of Down syndrome. The test also may indicate increased risk of defects in the neural tube, abdominal wall, or kidneys or risk of pregnancy complications. Because the calculation of risk is more reliable when performed in combination with the first trimester screening, it is important that both tests be performed in the same laboratory. 
  • Eligibility: The test is included in the health services basket and is performed in all HMO laboratories with a medical referral, with a partial deductible. 

NIPT/NIPS Test (test of the fetal chromosomes by testing the mother’s blood)

  • What is being tested: Test of the fetal DNA that is found in minute quantities in the mother’s blood. 
  • When the test is performed: The test may be performed from Week 10 of pregnancy. 
  • Purpose of the test: To identify fetuses at increased risk of Down syndrome. Abnormal results identify over 99% of fetuses with Down syndrome. The test is not diagnostic and is not a substitute for chorionic villi sampling (CVS) or amniocentesis. Any abnormal result must be confirmed through a diagnostic test (such as CVS or amniocentesis). 
  • Eligibility: The test is performed privately. Check with the HMO about partial funding through supplementary insurance or through private insurance. 

For more information about the NIPT/NIPS test,.

Ultrasound

Nuchal transparency

  • What is being tested: Every fetus has a small amount of fluid underneath the skin on the back of the neck. A correlation was found between the thickness of the fluid and the risk of Down syndrome. In this test, an ultrasound is performed to measure the fluid thickness in millimeters as well as fetal length from head to the end of the spine. The test also may indicate an increased risk of other fetal anomalies (primarily heart defects). 
  • When the test is performed: From Week 11 and until the end of Week 13 of pregnancy. 
  • Purpose of the test: The value obtained in the transparency measurement will be calculated with the age of the woman and the results of the first trimester blood tests, PAPP-A and HCG; the data obtained is the weighted risk (Combined Test) of the mother delivering a newborn with Down syndrome in comparison with the general risk of women in her age group. 
  • Eligibility: The test is included in the health services basket with a partial deductible. 
  • Important to know: In higher-order pregnancies, the risk of Down syndrome is calculated based on this test without weighing the blood screening tests.

For more information about the nuchal transparency test

Early anatomy scan

  • What is being tested: an ultrasound of the fetal organs and measurement of the fetus (such as circumference of the head, abdomen, etc.) designed to detect structural changes or defects in the early stages of pregnancy. 
  • When the test is performed: From Week 14 and until the end of Week 16 of pregnancy.
  • Purpose of the test: To detect fetal anomalies. The test can help detect suspicious findings that may indicate the presence of genetic syndromes, such as Down syndrome. If such a suspicion arises, the woman may be referred to genetic counseling and other diagnostic tests.
  • Eligibility: The test is not included in the health services basket unless there are special instructions to perform it. Check the participation of supplementary insurance.

Late anatomy scan

  • What is being tested: an ultrasound of the fetal organs and measurement of the fetus (such as circumference of the head, abdomen, etc.). The test is primarily to detect structural defects in the fetus.
  • When the test is performed: From Week 19 and until the end of Week 24 of pregnancy. The ideal date recommended is between Week 20 and Week 23 of pregnancy.
  • Purpose of the test: The test was not designed to determine the level of risk of Down syndrome, but in certain cases, the risk may be assessed based on abnormal findings or structural indications that arose during the test (in combination with the weighted screening).
  • Eligibility: The test is included in the health services basket.

Questions and Answers

These tests indicate the level of risk of having a newborn with Down syndrome or other defects. The results indicating a “high risk” do not definitively determine that the fetus has Down syndrome, and, in fact, most women deliver healthy infants even if the screening indicated a high risk. It should be noted that even when a low risk level is obtained, the fetus may have Down syndrome (or another disorder).

In the case of NIPT/NIPS, with any abnormal result, the chance of the fetus having Down syndrome is extremely high, but this must be confirmed through a diagnostic test (such as CVS or amniocentesis). 

The purpose of the tests is to identify pregnancies at high risk of a fetus with Down syndrome. 

Based on the level of risk, you can make a decision on whether to perform prenatal diagnosis by way of an invasive diagnostic test (CVS or amniocentesis).

In Israel, a high weighted risk for women in the general population is 1:380 births and higher (0.26%), while a low weighted risk is a result less than 1:380 births. If the results indicate a high weighted risk, a recommendation will be made that you undergo a diagnostic test—CVS or amniocentesis.

In this case, you will be referred to genetic counseling for continued examination and to decide whether to perform an invasive diagnostic test.

During the early stages of pregnancy (until the end of Week 13 of pregnancy) 

Nuchal transparency as well as first and second trimester blood tests should be performed. Depending on the risk level obtained, the performance of additional tests may be considered.

  • Risk level higher than 1:200—you will be referred to genetic counseling to consider undergoing a diagnostic test such as CVS or amniocentesis. 
  • Risk level between 1:201 and 1:3000—a recommendation will be made that you undergo an additional screening at the end of Week 16 of pregnancy to obtain a final risk assessment that is based on the results of all tests. If the risk level that is obtained after receiving all tests is greater than 1:380, you will be referred to genetic counseling to consider amniocentesis.
  • Risk level less than 1:3001: there is no need to continue examination for Down syndrome. 
  • The value of the nuchal transparency from 3 mm and higher constitutes in and of itself an increased risk for Down syndrome. In this case, you will be referred to genetic counseling and will receive a recommendation to perform a diagnostic test, such as CVS or amniocentesis (the tests are funded by the HMO).

During the later stages of pregnancy (from Week 14 of pregnancy) 

The triple test should be performed. Continued care will be determined based on the risk level that is obtained:

  • Risk level higher than 1:380—you will be referred to genetic counseling to consider amniocentesis.
  • Risk level less than 1:3001—the result is satisfactory, and there is no need to continue examination for Down syndrome.

For Your Information

For Your Information

Under any circumstance, the NIPT/NIPS test for Down syndrome in the fetus in testing the mother’s blood with high reliability may be considered. It is important to mention that this is not a diagnostic test and is not a substitute for an amniocentesis.

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