Screening for Down Syndrome: Nasal Bones

First-trimester noninvasive screening to detect Down syndrome relies on the measurement of fetal nuchal translucency (NT), serum pregnancy-associated plasma protein-A (PAPP-A), and maternal serum free β-human chorionic gonadotropin (β-hCG). A new marker — absence of nasal bones (NBs) — represents a logical addition to the screening, given that 50% of children with Down syndrome have nasal hypoplasia.

These authors studied the presence or absence of fetal NBs in 20,418 singleton pregnancies that were screened for trisomy 21 at 11 through 13 weeks’ gestation. Scans were performed by 33 different sonographers. The median maternal age was 35. Overall, the NB was absent in 238 fetuses (1.2%) and present in 19,937 fetuses (97.6%); it could not be …