Variation of fetal nasal bone length in second-trimester fetuses according to race and ethnicity.
OBJECTIVE
The purpose of this study was to determine the influence of race and ethnicity on the expected nasal bone length (NBL) based on biparietal diameter (BPD) measured in second-trimester fetuses.


METHODS
We searched our ultrasound, obstetric, and cytogenetic databases for all second-trimester fetuses with measured NBLs. Fetuses with Down syndrome were identified and excluded from the analysis. Linear regression curves were generated for NBL by BPD according to race and ethnicity. Categories used were African American, Hispanic, Asian, and white. Analysis of variance was used to compare mean variation of observed from expected NBL by BPD according to race and ethnicity.


RESULTS
There were 717 fetuses with NBL-by-BPD pairs who were available for analysis in our population, including 139 African American, 58 Hispanic, 22 Asian, and 498 white fetuses. Nasal bone length was highly correlated with BPD for each race (P < .001). Mean variances of observed from expected NBL by BPD were statistically different according to race or ethnicity (P = .0092).


CONCLUSIONS
Race and ethnicity significantly affect the mean regression line of expected NBL by BPD among fetuses in the second trimester. Genetic sonographic norms, therefore, appear to require race- and ethnicity-specific formulas for NBL.
Zelop
Carolyn M
CM
Department of Obstetrics and Gynecology, Saint Francis Hospital and Medical Center, 114 Woodland St, Hartford, CT 06105 USA. czelop@stfranciscare.org
Milewski
Elizabeth
E
Brault
Kimberly
K
Benn
Peter
P
Borgida
Adam F
AF
Egan
James F X
JF
D001741:Black or African American; D001213:Asian; D005260:Female; D005865:Gestational Age; D006630:Hispanic or Latino; D006801:Humans; D009295:Nasal Bone / Q000000981:diagnostic imaging* / Q000196:embryology*; D011247:Pregnancy; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal; D044465:White People