Article|Articles in Press, 100879

Performance of prenatal cfDNA screening for sex chromosomes

Open AccessPublished:May 05, 2023DOI:
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      To assess the performance of cell-free DNA (cfDNA) screening to detect sex chromosome aneuploidies (SCA) in an unselected obstetrical population with genetic confirmation.


      This was a planned secondary analysis of the multicenter, prospective SMART study. Patients receiving cfDNA results for autosomal aneuploidies and who had confirmatory genetic results for the relevant sex chromosomal aneuploidies were included. Screening performance for SCAs, including monosomy X (MX) and the sex chromosome trisomies (SCTs; 47,XXX; 47,XXY; 47,XYY) was determined. Fetal sex concordance between cfDNA and genetic screening was also evaluated in euploid pregnancies.


      17,538 cases met inclusion criteria. Performance of cfDNA for MX, SCTs and fetal sex was determined in 17,297, 10,333 and 14,486 pregnancies, respectively. Sensitivity, specificity, and PPV of cfDNA were 83.3%, 99.9%, and 22.7% for MX, and 70.4%, 99.9%, and 82.6% for the combined SCTs. The accuracy of fetal sex prediction by cfDNA was 100%.


      Screening performance of cfDNA for SCAs is comparable to that reported in other studies. The PPV for the SCTs was similar to the autosomal trisomies, while the PPV for MX was substantially lower. No discordance in fetal sex was observed between cfDNA and postnatal genetic screening in euploid pregnancies. These data will assist interpretation and counseling for cfDNA results for sex chromosomes.