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

We sought to compare the fetal nasal bone length (FNBL) between different ethnic groups at 11-14 weeks' gestation.

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.

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.

If the FNBL is to be introduced into first-trimester screening, it should be adjusted for ethnicity.