Prenatal screening for trisomy 21 (Down syndrome) using first- and second-trimester biochemistry and nuchal translucency: A technical standard of the American College of Medical Genetics and Genomics (ACMG).

This technical standard was developed as a guide for laboratories performing prenatal screening for Down syndrome. It addresses 3 topics: second trimester (triple or quad), first trimester, including incorporation of nuchal translucency, and current directions in cell-free DNA screening. Analytic methods, clinical considerations, screening performance, guidelines for reporting second trimester, first trimester, integrated, contingent, and reflex screening tests for Down syndrome, are discussed. Individual laboratories are responsible for meeting the quality assurance standards described by the Clinical Laboratory Improvement Amendments, the College of American Pathologists, and other regulatory agencies, with respect to appropriate sample documentation, assay validation, general proficiency, and quality control measures.