Nasal bone length at 11-14 weeks of pregnancy in the Korean population.

OBJECTIVES

The aim of this study was to provide reference values for nasal bone length (NBL) scanned at 11-14 weeks' gestation in the Korean population and compare these values with those of the Caucasian and African-American populations.

METHODS

From April 2004 to July 2004, fetal NBLs were measured in well-dated, non-anomalous fetuses at 11-14 weeks' gestation in the Korean population. Regression analysis was used to assess the relationship between NBL and crown-rump length (CRL), and reference values including the 5th, 50th, and 95th percentile were calculated for each gestational age. The reference values in our study were compared with those of the Caucasian and African-American populations.

RESULTS

A total of 982 cases were prospectively included in the study. NBL increased linearly with advance in CRL and was described by the equation; NBL (mm) = 0.433 + 0.022 x CRL (mm), R(2) = 0.37. The median values (5%, 95%) were 1.5 mm (1.2 mm, 1.9 mm), 1.7 mm (1.4 mm, 2.1 mm), 1.9 mm (1.6 mm, 2.3 mm), and 2.1 mm (1.7 mm, 2.6 mm) for 11, 12, 13, and 14 weeks' gestation, respectively. The median values for each gestational age in the Korean population were significantly lower than those in the Caucasian and African-American populations (P < 0.0001).

CONCLUSION

There is a difference in NBL scanned at 11-14 weeks' gestation between the Korean and the Caucasian/African-American populations, and so racial adjustment is needed in the evaluation of the fetal nasal bone for current first-trimester screening.