Reference values for the length and area of the fetal corpus callosum on 3-dimensional sonography using the transfrontal view

Objectives: The purpose of this study was to determine reference values for the length and area of the fetal corpus callosum between 20 and 33 weeks' gestation using 3-dimensional sonography. Methods: A cross-sectional study was performed in 293 healthy pregnant women between 20 and 33 weeks' gestation. The length and area of the corpus callosum were obtained via the transfontal view with the metopic suture as an acoustic window using 3-dimensional sonographic aquisitions. Linear and weighted polynomial regression models were used, which were adjusted by residual analysis and the R2 determination coefficient. Intraobserver and interobserver reproducibilities were analyzed by an intraclass correlation coefficient. Results: The mean corpus callosum length ± SD varied from 19.52 ± 2.24 to 40.36 ± 2.87 mm, whereas the mean area varied from 0.44 ± 0.11 to 1.47 ± 0.21 cm² at 20 and 33 weeks, respectively. The length and area were highly correlated with gestational age: corpus callosum length = -52.41 + 4.71 × gestational age - 0.06 × gestational age² (R² = 0.868); and corpus callosum area = -2.47 + 0.16 × gestational age - 0.000037 × gestational age² (R² = 0.765). The intraobserver and interobserver reproducibilities were excellent, with intraclass correlation coefficients of 0.98 and 0.94 for the length and 0.99 and 0.90 for the area, respectively. Conclusions: Reference values for the length and the area of the fetal corpus callosum between 20 and 33 weeks' gestation were determined with high reproducibility.