Reference Intervals for Fetal Ear Length Between 19 and 24 Weeks of Pregnancy on 3-Dimensional Sonography

Abstract

The purpose of this study was to establish reference intervals for fetal ear length using 3-dimensional sonography in the rendering mode. A cross-sectional study was conducted on 114 women from 19 weeks to 23 weeks 6 days of normal pregnancy. Fetal ear length measurement was performed in the rendering mode, obtained from 2-dimensional mode reconstruction. To determine the correlation between ear length and gestational age, scatterplots were constructed, and the Pearson correlation coefficient was calculated. Mean, median, SD, maximum, and minimum values and percentiles for each gestational age were calculated. To calculate the intraobserver reproducibility, we used the intraclass correlation coefficient. The mean ear length ± SD increased from 14.43 ± 1.28 mm (range, 12.80-16.50 mm) in the 19th week of pregnancy to 19.72 ± 1.87 mm (range, 17.20-22.40 mm) in the 23rd week. Three-dimensional sonographic ear length measurements were correlated with gestational age, with the best adjustment represented by the following exponential equation: ear length = exp(1.215 × gestational age - 8.692) (R(2) = 0.423). The intraobserver reproducibility was excellent, resulting in an intraclass correlation coefficient of 0.967 (95% confidence interval, 0.939-0.982). Reference intervals for fetal ear length using 3-dimensional sonography in the rendering mode from 19 weeks to 23 weeks 6 days of pregnancy were determined and proved reproducible.