What is a Down Syndrome Screening?

Question

What is a Down Syndrome Screening?

Answer

A Down syndrome screening, often abbreviated as ‘Down screen,’ is a prenatal test designed to assess the risk of the fetus having Down syndrome (trisomy 21). This test is typically conducted during the second trimester, around the 15th to 20th week of pregnancy. The purpose of the Down syndrome screening is to calculate the risk of the fetus having Down syndrome by testing for certain proteins and hormone levels in the pregnant woman’s blood. These tests include measuring levels of alpha-fetoprotein (AFP), a specific form of human chorionic gonadotropin (hCG), and fetal DNA levels. The results of the Down syndrome screening are presented as a risk score, usually with a range indicating high or low risk. High-risk results suggest a greater chance of the fetus having Down syndrome, while low-risk results indicate a lower chance. It’s important to note that the Down syndrome screening is not a diagnostic test; it only provides an assessment of risk to parents. If the screening result shows a high risk, further diagnostic tests may be recommended, such as amniocentesis or chorionic villus sampling. Please be aware that the accuracy of the Down syndrome screening is not 100%, and there can be false positive or false negative results. Additionally, even if the screening result is normal, it does not completely rule out the possibility of the fetus having Down syndrome or other chromosomal abnormalities. Therefore, the Down syndrome screening should be combined with other diagnostic methods.