P08.20: Fetal nasal bone length at 16th–23rd gestational weeks: a study from Ankara, Turkey

Abstract

Objectives: Hypoplasia of the nasal bone is an important ultrasound marker for Down syndrome in the second trimester. Racial differences in fetal nasal bone length have been reported. However, there is no reference range for the fetal nasal bone length (NBL) in Turkish population. The aim of this study was to investigate the reproducibility of fetal NBL measurement in the mid second. trimester and to determine normogram for NBL between 19–23 weeks of gestation in the Turkish population. Methods: A total of 757 fetuses were evaluated between January 2009 and February 2010. Ultrasound measurements of NBL were performed on a strictly sagital plane with an insonation angle less than 30 degrees. The relationship between NBL and gestational age was determined and percentile values for each gestational week were calculated. The relationship between NBL and biparietal diameter was evaluated by Pearson correlation analysis. One way anova was used to assess the differences between the NBL and gestational age. Results: There was no significant relationship between NBL and biparietal diameter (r = 0.021 ve P = 0.634). The mean NBL was 5.7 mm ± 0.68 for 19–19+6/7 weeks, 6.1 mm ± 0.72 for 20–20+6/7 weeks, 6.4 ± 0.86 mm for 21–21+ 6/7 weeks, 6.5 mm ±1.01 for 22–22+6/7 weeks and 7.2 mm ± 0.98 for 23–23+6/7 weeks’ gestation. The measurements of NBL showed a significant increase with gestational age (P = 0.001). Conclusions: We have provided the normal reference range for NBL during the 19–23 weeks in Turkish population.