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.