Trisomy 21 (T21) is the most common chromosomal abnormality, affecting 1:800 live births. Despite increased use of ultrasonography and serum biomarker screening for T21, invasive testing (chorionic villus sampling [CVS] or amniocentesis) is still required in 3% to 5% of patients and has a miscarriage risk of approximately 1%.¹ In 1997, cell-free DNA (cfDNA) fragments from the fetus were discovered in maternal plasma but in a relatively small proportion, limiting clinical use.² The advent of massively parallel sequencing (MPS) technology enabled amplification of cfDNA, but application of this method for T21 screening had only been demonstrated in small cohort studies previously.

To determine the accuracy and feasibility of MPS of maternal DNA for use in prenatal screening for T21 in high-risk pregnancies.