Objective: Examine whether repeat nasal bone evaluation following an absent/uncertain nasal bone on first-trimester screening (FTS) improves Down syndrome (DS) screening specificity.
Methods: A retrospective chart review of FTS sonograms in one center from January 2015 to January 2018 was performed. Data was extracted for those with an absent/uncertain nasal bone. Repeat evaluations were offered.
Results: Of 6780 FTS sonograms, 589 (8.7%) had an absent/uncertain nasal bone. Upon repeat exam, 268/376 (71.3%) had a present nasal bone. Compared with Black patients, patients of other ethnicities were more likely to have a present nasal bone on exam 2 (P < .00001). Of 268 patients with a present nasal bone on exam 2, 37 (13.8%) had an abnormal DS risk following exam 1; 34/37 (91.9%) normalized following nasal bone visualization, dropping the screen positive rate to 1.1%.
Conclusion: Repeat nasal bone examination is beneficial in refining DS risk assessment and improves the specificity of FTS.
Keywords: Down syndrome screening; first-trimester screening; nuchal translucency ultrasound; prenatal ultrasound.
© 2023 American Institute of Ultrasound in Medicine.