OP04.13: Fetal feet length differences between three‐dimensional and two‐dimensional ultrasound measurements

Abstract

Three-dimensional (3D) ultrasound (US) is the ideal tool in complementing two-dimensional ultrasound (2D US) for the evaluation of fetal extremities. The purpose of this study was to investigate the accuracy of 3D and 2D ultrasound measurements of the fetal feet length during second trimester of gestation. Twenty three consecutive women underwent ultrasound examination for different indications at 14–25 weeks of gestation formed the study cohort. Fetuses with known congenital malformations, chromosomal abnormalities or abnormal fetal growth were excluded. After standard 2D US was performed, the same sonologist also obtained 3D volumes. VOLUSON 730 ultrasound equipment (General Electrics, GE Healthcare, Milwaukee, Wisconsin, USA) was used for all for all US examinations. We performed axial scans of the fetal foot. The foot length was measured from the heel to the first, or second toe, whichever was longer. The paired t test was used in the comparison of the 2D measurements and the 3D measurements of fetal feet length. The difference was considered to be significant when the p value was less than 0.05. Mean fetal feet length was found to be longer in the 2D US measurement than 3D US measurement (mean ± standard deviation: 32.0 ± 12.2 mm versus 30.5 ± 11.2 mm, respectively). Distribution of the fetal feet length differences between 3D and 2D US sans was significant (P = 0.007) (Fig). Figure. Relationship between fetal foot length measurement by 3D US (rounds) and 2D US results at 14–25 weeks of gestation in 23 fetuses. The diagonal line is the reference line (fetal foot length measurement by 2D US). Surprisingly, sonographic estimation of fetal feet length were found to be statistical significantly longer in 2D US than 3D US questioning the accuracy of present 2D obtained reference values on 3D measurements. Further studies are required to asses the reproducibility of this difference.