Nasal bone length throughout gestation: normal ranges based on 3537 fetal ultrasound measurements

Objective: To establish normal ranges for nasal bone length measurements throughout gestation and to compare measurements in two subsets of patients of different race (African-American vs. Caucasian) to determine whether a different normal range should be used in these populations.

Method: Normal nasal bone length reference ranges were generated using prenatal measurements by a standardized technique in 3537 fetuses.

Results: The nasal bone lengths were found to correlate positively with advancing gestation (R(2) = 0.77, second-order polynomial). No statistical difference was found between African-American and Caucasian subjects.

Conclusion: These reference ranges may prove to be useful in prenatal screening and diagnosis of syndromes known to be associated with nasal hypoplasia. Different normal ranges for African-American and Caucasian women are not required.