Prenatal screening for trisomy 21: recent advances and guidelines.

The performance of prenatal screening tests for the identification of trisomy 21 (Down syndrome) has markedly improved since the 1970s and early 1980s when maternal age was the sole mode of screening the general pregnant population. With the discovery of second trimester serum markers in the 1980s and 1990s and implementation of double, triple, and quad marker testing; the discovery of first trimester serum and ultrasound markers in the 1990s and implementation of the combined test; and the development of the integrated test and sequential screening strategies over the past decade, the performance of screening has improved to a detection rate of 90%–95% at a false positive rate of 2%–5%. In this review, I will describe the advances in prenatal screening for trisomy 21, present current screening strategies, and discuss guidelines published by professional societies and regulatory bodies, with a focus on current prenatal screening practice in the USA.