Ethnic variation of fetal nasal bone length between 11–14 weeks' gestation

Objective We sought to compare the fetal nasal bone length (FNBL) between different ethnic groups at 11–14 weeks' gestation. Methods FNBL and the FNBL/CRL ratio were measured in patients undergoing first trimester ultrasound for nuchal translucency (NT) and the ethnicity of the patient was recorded under four categories: non‐Hispanic White, non‐Hispanic black, Hispanic, and Chinese. Results Two hundred and one patients were included in the study. Measurement of the FNBL could not be obtained in nine patients (4.5%) and foetal nasal bone was absent in one fetus. Comparing the four groups, non‐Hispanic White, non‐Hispanic Black, Hispanic, and Asian, there were no statistical differences in crown‐rump length (61 ± 14 mm; 68.6 ± 15 mm; 60.2 ± 14 mm; 62.4 ± 8.8 mm, respectively) or the NT (1.3 ± 0.5 mm; 1.25 ± 0.4 mm; 1.35 ± 1 mm; 1.4 ± 0.4 mm, respectively). However, the FNBL (2.9 ± 0.7 mm; 2.5 ± 0.6 mm; 2.5 ± 0.6 mm; 2.2 ± 0.4 mm, respectively, p < 0.01) and the FNBL/CRL ratio (0.049 ± 0.01, 0.045 ± 0.01, 0.043 ± 0.01, 0.037 ± 0.01, respectively, p < 0.01) were both statistically different, when comparing between these groups. Conclusion If the FNBL is to be introduced into first‐trimester screening, it should be adjusted for ethnicity. Copyright © 2005 John Wiley & Sons, Ltd.