Prenatal Screen for Rare Chromosome Abnormalities Confirms Fetal Diagnosis in Only 5 Percent of Positive Cases
A single-center study in China tracked 64,889 singleton pregnancies screened by genome-wide noninvasive prenatal testing between March 2021 and July 2024. Of 112 pregnancies flagged for rare autosomal trisomies, 79 underwent invasive diagnostic testing. Only 5.1 percent were confirmed in the fetus. When uniparental disomy and runs of homozygosity findings were included, the diagnostic yield rose to 8.9 percent. Follow-up of 104 pregnancies found 63 uncomplicated outcomes, 34 adverse pregnancy outcomes, and 7 terminations. Researchers tested whether a sequencing metric called theoretical mosaicism ratio could predict adverse outcomes. The metric showed poor discrimination overall, with an area under the curve of 0.643. A ratio of 0.63 or higher was associated with adverse outcomes after adjustment, but overlap and poor performance limit its use as a standalone predictor.
Positive noninvasive screening results for rare trisomies carry meaningful pregnancy risk even when fetal confirmation rates are low. Sequencing-derived metrics must be interpreted alongside chromosome analysis, ultrasound, and clinical findings rather than used alone.
Written by the Genomes desk from the primary source linked above and checked against it. Research use only; not medical advice. Corrections: [email protected].