What screening test is performed at 15-20 weeks to assess risks for Down syndrome?

The screening test performed at 15-20 weeks to assess risks for Down syndrome is the quad screen test. This test measures the levels of four substances in a pregnant woman's blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), estriol, and inhibin A. Abnormal levels of these markers can indicate an increased risk for chromosomal abnormalities, including Down syndrome (trisomy 21).

The quad screen is a non-invasive screening that provides valuable information and can help guide further diagnostic testing if the risk appears elevated. It’s commonly offered to expectant mothers as part of routine prenatal care, and optimal timing within the 15-20 week window allows for accurate assessment.

While other options such as chorionic villus sampling and amniocentesis are diagnostic tests used to definitively confirm genetic conditions, they are generally performed later in the pregnancy. Hemoglobin tests are typically used to check for anemia rather than for genetic screening. Thus, the quad screen is specifically designed for early maternal serum screening for Down syndrome risk, making it the correct choice in this context.