P01.05: The effect of ethnicity on first‐trimester nasal bone assessment

Abstract

To determine whether first-trimester nasal bone assessment varies with ethnicity. Nasal bone was prospectively evaluated in 5,193 patients undergoing first-trimester combined ultrasound and biochemical screening in the United States. Among these patients 19 had absent nasal bone and in 1075 patients nasal bone length was evaluated. Nasal Bone length was adjusted for gestational age and the nasal bone MoM values were then compared with maternal weight and ethnicity. Median nasal bone MoM vales for ethnic groups were compared using the Kruskal-Wallis test. ×CRL.6415. Using this formula, expected nasal bone length was 1.6 at 45 CRL and 2.3 at 84 CRL. The correlation of maternal weight with nasal bone MoM was statistically (P = 0.036) but not clinically significant. Expected nasal bone MoM = 0.96,1.02,1.06 at 100, 200 and 300 lbs., respectively. The median nasal bone MoM was 0.98 for Caucasions (n = 766), 0.99 for African Americans (n = 45), 1.02 for Asian Indians (n = 52), 0.98 for Asians (n = 65), 1.00 for Hispanics (n = 82) and 1.00 in others (n = 65). The differences were not significant (P = 0.779). The rate of absent nasal bone was 13/3835 (0.3%), 0 of 266 (0.0%), 2 of 152 (1.3%), 1 of 313 (0.3%), 3 of 343 (0.9%), 0 of 284 (0.0%) for the Caucasian, African American, Asian Indian, Asian, Hispanic and Other ethnic groups, respectively. Nasal bone was absent in 13/3835 (0.3%) Caucasian, 0/266 (0.0%) African American, 2/152 (1.3%) of Asian Indian, 1/313 (0.3%) Asian, 3/343 (0.9%) Hispanic and 0/284 (0%) Other ethnic groups. These percentages were not significantly different (X2 = 8.3, P = 0.140). The data indicate that any differences in nasal bone length or absent/presence amongst the various ethnic groups are likely to be insignificant or can be accounted for with minor adjustments.