cfDNA residual risk review

A narrative review asking what clinically significant fetal abnormality remains after a low-risk cell-free DNA result for the common trisomies, and how much of that residual burden is identified by the 11 to 13 week ultrasound assessment. Five evidence domains will be addressed: chromosomal abnormalities outside the cfDNA report, pathogenic copy number variants where the scan is normal, increased nuchal translucency with normal genetics, non-chromosomal structural abnormality, and rare autosomal trisomies, failed tests and monogenic disorders. Screening is performed independently in duplicate. This project holds the protocol, the search strategies, the screening records, the extraction forms and the deviations log.