What screening test is performed to assess the risk of Down syndrome during the first trimester?

The screening test performed to assess the risk of Down syndrome during the first trimester is the nuchal translucency ultrasound combined with serum markers. This test typically involves a specialized ultrasound that measures the thickness of the nuchal fold at the back of the baby’s neck. Increased thickness can be associated with an elevated risk for Down syndrome.

In addition to the ultrasound measurement, maternal blood is also tested for specific markers, such as pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG). By combining these ultrasound findings with the serum marker results, healthcare providers can calculate a risk factor for Down syndrome and other chromosomal conditions.

Other screening methods mentioned, such as amniocentesis and chorionic villus sampling (CVS), are invasive diagnostic procedures typically performed later in pregnancy to obtain a definitive diagnosis of genetic conditions, rather than initial screening. The quad screen test, conducted during the second trimester, assesses different markers for Down syndrome and other conditions but is not specific to the first trimester. Therefore, the nuchal translucency ultrasound combined with serum markers is the appropriate first-trimester screening test for assessing the risk of Down syndrome.