Ultrasonographic evaluation of fetal nasal bone in a low-risk population at 11-13 + 6 gestational weeks

Abstract

Objective: To evaluate the utility of determining the presence/absence of nasal bone in a low-risk fetal population.

Methods: Prospective study of the presence/absence of nasal bone among 1800 consecutive unselected fetuses, with complete follow-up of results.

Results: An adequate sonographic evaluation of nasal bone was obtained in 1682 (93.44%) of the fetuses. Nasal bone was considered absent in 19 (1.06%) of 1790 fetuses with a normal karyotype and in 2 (28.57%) of the seven recorded cases of Down syndrome (DS). The overall first-trimester sensitivity for DS to the absence of nasal bone was two of the six cases (33.3%) and the false-positive rate was 1.13%. The positive predictive value for DS of the absence of nasal bone was 2/21 (9.52%).

Conclusions: In a low-risk population, the evaluation of the presence/absence of nasal bone in DS screening during the first trimester has a low sensitivity. First-trimester assessment of the nasal bone in population screening may play a lesser role than in the re-evaluation of high-risk pregnancies.