RESUMO
The aim of the present cross-sectional study is to define the reference range for the nuchal translucency (NT) measurements in normal Korean fetuses between 10 and 14 weeks' gestation. The nuchal translucency was measured prospectively in 202 chromosomally normal singletons of women attending our antenatal clinic or prenatal diagnostic center by 177 transabdominal sonography (88%) and by 25 transvaginal sonography (12%) if difficulty was encountered with transabdominal sonography. The NT measurement was expressed as the median and 5th, 95th centiles according to crown-rump length (CRL) measurements by ultrasound. Mean multiple of median (MoM) and the 95th centile of MoM values of the NT measurements with CRL in 10 mm intervals were also calculated. NT measurements increased significantly with CRL[NT (mm)=0.481647+0.020142xCRL (mm)]. A NT measurement greater than 2.5 mm was found in 4% of normal fetuses, but this proportion increased form 0% at 10-11 weeks, to 3.8, 8.8, 11.5% at 12, 13, 14 weeks, respectively. The present study provides normative data on the fetal NT thickness in a Korean population, which may improve the performance of NT screening for chromosomal abnormalities in the first trimester.