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First-trimester biochemical screening tests include a combination of nuchal translucency ultrasound (ultrasound) with biochemical screening tests - PAPP-A (Pregnancy-associated Plasma Protein-A) and Free Beta HCG (Human Chorionic Gonadotropin).
First-trimester screening tests include the nuchal translucency ultrasound combined with biochemical screening tests, which measure the levels of PAPP-A and free beta-hCG in the blood. When these tests are analyzed together with the mother's age at the expected time of birth, the statistical predictive ability for assessing pregnancy health increases to over 80%.
The screening tests for assessing the risk of Down syndrome ("nuchal translucency," "first-trimester screen," "combined risk assessment," "triple/quadruple screen," and sonographic markers) estimate the statistical risk of Down syndrome and do not confirm or rule out the syndrome. Therefore, any result that deviates from the norm should be discussed with the attending obstetrician and, if necessary, with a genetic counselor.
PAPP-A is a protein produced normally by the placenta during pregnancy. According to medical literature, the risk of Down syndrome increases as the PAPP-A level decreases.
BHCG is a hormone produced normally by the placenta during pregnancy. According to medical literature, the risk of Down syndrome increases as the BHCG level increases.
It's important to understand that statistical screening is not a diagnostic test (meaning it does not provide a "yes" or "no" answer) but allows for a statistical calculation of risk. For example, a risk of 1:400 means that out of 400 pregnancies with this result, one will be affected, and 399 will be healthy.
The comparison is made to the likelihood of a woman aged 35 or older having a child with Down syndrome. When the results of first-trimester screening tests are "normal," the risk of having a child with Down syndrome is lower than the risk for a woman aged 35 or older during pregnancy. When the results are "abnormal," the risk is higher than for a woman aged 35 or older during pregnancy. However, it's important to note that an abnormal result does not necessarily mean that the fetus has Down syndrome, and most fetuses with abnormal blood screening results will still be healthy.
Yes, by performing second-trimester biochemical screening tests (triple screen) and combining all results into one, you can achieve a high detection rate (over 90%). In this case, you will receive the results of both first and second-trimester screening tests together.
The test should be performed between 11+0 and 13+6 weeks of pregnancy, until the fetus reaches a crown-rump length (CRL) of 84 mm. Performing the test outside these timeframes may complicate result comparisons to those of a healthy population.
This test is considered the most accurate non-invasive method for assessing the risk of Down syndrome. It combines the results of both first and second-trimester screening tests, the mother's age, nuchal translucency measurement, and biochemical markers (PAPP-A, AFP, hCG, uE3, inhibin-A). The calculated risk provides a detection rate of over 90%.
This method is particularly useful for women at low risk for Down syndrome (according to age) because the triple screen ("biochemical screen") detects only about 60% of fetuses with Down syndrome (compared to about 70% in high-risk women).
The "Integrated Risk" test can be used for women over the age of 35 who do not wish to undergo invasive testing, such as chorionic villus sampling (CVS) or amniocentesis, despite the recommendation of the Israeli Ministry of Health for women over 35 to undergo CVS or amniocentesis.
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