What is the normal range for唐screen values?
Sep 13, 2022
Source: Cainiu Health
Dr. Lv Aiming
Introduction
The normal value for Down syndrome screening should be less than 1/260. Down syndrome screening is a test performed during the second trimester of pregnancy, with a cutoff threshold of 1/260; values above this indicate a higher risk. This screening measures levels of alpha-fetoprotein and unconjugated estriol in the pregnant woman's blood, and assesses the risk of Down syndrome based on the mother's weight, age, and gestational age, thereby determining the likelihood of the condition.
Down syndrome screening generally refers to testing performed between weeks 16 and 18 of pregnancy. So, what is the normal range for Down syndrome screening results?
What Is the Normal Range for Down Syndrome Screening?
The normal value for Down syndrome screening should be less than 1/260. This screening is a second-trimester prenatal test with a cutoff threshold of 1/260; values above this indicate a higher risk. The test involves collecting a blood sample from the pregnant woman between weeks 15 and 20 of pregnancy. By measuring levels of alpha-fetoprotein (AFP) and unconjugated estriol (uE3) in maternal blood, and considering factors such as the mother's weight, age, and gestational age, the test estimates the risk of Down syndrome and determines the likelihood of the condition.
The high-risk value in early唐 (first-trimester combined screening) is calculated by multiplying individual risk factors such as maternal age, PAPP-A MoM value, and NT measurement. If the NT measurement is less than 3 mm, even if the early screening indicates elevated risk, the expectant mother can generally feel reassured, as NT measurements carry greater clinical significance. If concerns persist, non-invasive prenatal testing (NIPT) can be considered. When the NT measurement exceeds 3 mm, in addition to chromosomal abnormalities, other conditions associated with increased NT—such as congenital heart defects—should also be evaluated. Under medical guidance, it may be necessary to undergo amniocentesis to diagnose potential chromosomal issues.
Down syndrome screening results only predict the probability of occurrence and cannot provide a definitive diagnosis. Confirmation requires diagnostic procedures such as amniocentesis or non-invasive DNA testing. During pregnancy, it’s important to follow medical advice, make scientifically informed preparations, and pay attention to proper nutrition and healthy lifestyle habits. We hope this information has been helpful. Wishing you good health and happiness!
