Abstract
BACKGROUND: Prenatal cell-free DNA (cfDNA) screening has transformed the prenatal aneuploidy testing landscape testing since its clinical introduction in 2011. Leveraging placentally derived cfDNA fragments as fetal indicators in maternal plasma, cfDNA screening enables highly sensitive aneuploidy detection, most notably for trisomies 21, 18, and 13. With its superior performance compared to traditional screening approaches, cfDNA screening has been rapidly adopted into routine obstetric care worldwide. CONTENT: This review provides an overview of central laboratory foundations of prenatal cfDNA screening based on our in-house developed test experience and includes preanalytical, analytical, and postanalytical considerations. Key topics include specimen handling, quality management practices, an overview of assay platforms, and bioinformatic processing. We explore test performance characteristics such as sensitivity, specificity, and positive predictive value (PPV), as well as factors influencing test accuracy. We discuss critical topics such as interpreting discordant results, the significance of low fetal fraction, and the challenges of confined placental mosaicism and maternal health conditions, including malignancy. Additionally, we consider cfDNA screening expansion to genome-wide analysis with associated interpretive complexities. SUMMARY: Prenatal cfDNA screening has quickly become a cornerstone of modern prenatal care. Accurate test performance requires rigorous assay validation, quality assurance, and clear interdisciplinary communication. Understanding laboratory methods and limitations underlying tests is essential for accurate interpretation and appropriate clinical integration. This review highlights the rapid evolution of testing and its profound impact on prenatal screening. As adoption expands and clinical guidelines evolve, the laboratory role in ensuring analytical quality and accurate result interpretation is critical.