label: Hypoplasia of fetal nasal bone
label_lc: hypoplasia of fetal nasal bone
description: "On prenatal ultrasound, the nasal bone is a thin echogenic line within the bridge of the fetal nose. The fetus is imaged facing the transducer with the fetal face strictly in the midline. The angle of insonation is 90 degrees, with the longitudinal axis of the nasal bone as the reference line. Calibres are placed at each end of the nasal bone. Absence of the nasal bone or measurements below 2.5th percentile are considered significant (PMID:16100637)."