Which test screens for fetal down syndrome during the first trimester?

The first-trimester screening, specifically the nuchal translucency measurement, is the test that screens for fetal Down syndrome during the early stages of pregnancy. This assessment is typically performed between 11 and 14 weeks of gestation and involves an ultrasound to measure the thickness of the nuchal fold at the back of the fetal neck. An increased nuchal translucency can indicate a higher risk of Down syndrome and other chromosomal abnormalities.

This test is often combined with maternal serum markers such as free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A) to improve the accuracy of the screening results. It’s significant because early detection allows for more informed decision-making and additional testing, if necessary.

In contrast, the triple screen and quad screen tests are performed in the second trimester (usually between 15 and 20 weeks of gestation) and evaluate different markers for assessing the risk of Down syndrome, but they do not occur in the first trimester. The expanded carrier screening is a genetic test aimed at identifying carriers of specific genetic conditions, and while it’s an important part of prenatal care in some cases, it does not specifically screen for Down syndrome.