SCREENING FOR DOWN SYNDROME: WHAT YOU NEED TO KNOW

Dr. Claude Allouche, Gynecologist Depistage T21 english
Ahuza Clinic, Raanana
058 726 02 64

Integrated screening for Down syndrome is a prenatal test designed to assess the risk that a fetus may have Down syndrome (Trisomy 21).

The test is performed in two stages:

STAGE 1 (11-13 weeks):

  • An ultrasound of the fetus's neck is performed to measure the thickness of the nuchal translucency. This is done by a specialized sonographer and is called in Hebrew “shkifout orpit” (שקיפות עורפית).

  • A blood test is then done immediately after the ultrasound to measure certain hormones in the maternal blood (PAPP-A and free beta HCG). This is called in Hebrew “seker biokhimi shlish rishon” (סקר ביוכימי שליש ראשון).

  • A calculation is made combining the mother's age, the measurement of the fetal neck, and the hormonal test results to estimate the risk of Down syndrome.

  • Both the ultrasound and the blood test must be done between 11 weeks of amenorrhea and 13 weeks + 6 days.

STAGE 2 (16-20 weeks):

  • A second blood test is done to measure levels of one hormone (Estriol) and two specific proteins in the maternal blood: human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP).

  • These results are combined with those from Stage 1 to refine the estimate of the risk of Down syndrome.

  • This blood test is called:

    • In French, "second trimester serum screening" or "triple test."
    • In Hebrew, “seker biokhimi shlish sheni” (סקר ביוכימי שליש שני) or “helbon oubari” (חלבון עוברי).

CAUTION! HIGH RISK?

If the risk is considered high, with the limit set in France at 1/250 and in Israel at 1/370, more invasive tests, such as a chorionic villus biopsy or amniocentesis, may be recommended to confirm the Down syndrome diagnosis.

LIMITATIONS OF THE TEST:

It is important to understand that integrated screening for Down syndrome cannot diagnose the condition with certainty. It only provides an estimate of risk. Therefore, it is essential to discuss the results and follow-up options with a healthcare professional.

What is NIPT?

  • If the risk is intermediate, a non-invasive maternal blood test called NIPT (Non-Invasive Prenatal Test) can also be performed.

  • This test is reliable but not as comprehensive as amniocentesis, as it only screens for Down syndrome, Trisomy 18, Trisomy 13, and a few other chromosomal abnormalities.

  • Its advantage is that it is not dangerous since it cannot cause a miscarriage like amniocentesis (although the risk is very low with amniocentesis).

  • Its disadvantage is the cost, which ranges from 3000 to 4000 shekels.

  • It should be noted that recently, in France, this test is reimbursed by Social Security if the risk from serum screening is estimated between 1/100 and 1/1000.

  • In Israel, it is not covered by the health funds, but it may be reimbursed by private insurance if you have subscribed to it prior to pregnancy.

YOUR DECISION, YOUR CONTROL:

Screening is not mandatory. The decision to undergo screening should be made by the pregnant woman after receiving complete information on the benefits and risks of the test.

REQUIRED MEDICAL EXPERTISE:

Screening for Down syndrome is a medical procedure that must be performed by a qualified healthcare professional. The choice of professional is essential to ensure the reliability of the results.

Take the time to think and gather all the necessary information before deciding to proceed with the screening.
Your health and that of your baby are a priority.

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