The impact of HBB-related hemoglobinopathies carrier status on fetal fraction in noninvasive prenatal screening.

Carriers of pathogenic variants in the HBB gene, but not the HBA1/HBA2 genes, are more likely to have lower FF when compared to women with structurally normal hemoglobin. This decrease in FF could result in an elevated test-failure rate if FF thresholds were used.