Development of the human fetal corpus callosum: A high-resolution, cross-sectional sonographic study

Objective: To establish reference ranges during human pregnancy for normal fetal corpus callosum dimensions. Design: In a prospective, cross-sectional study of 258 fetuses between 16 and 37 weeks of gestation, measurements of the length, width, and thickness at the level of the anterior mid-body of the corpus callosum were performed, using high-resolution, transvaginal and transabdominal transducers. Results: The mean length of the corpus callosum was 27.2 (standard deviation, 1.2; 95% confidence interval, 26.02-28.37) mm. Width and thickness of the corpus callosum were 5.6 (standard deviation, 1.6; 95% confidence interval, 5.41-5.82) mm and 1.9 (standard deviation, 0.7; 95% confidence interval, 1.87-2.06) mm, respectively. The size of the corpus callosum as a function of gestational age was expressed by regression equations: length (mm)=-20.40+1.92× gestational age; width (mm)=-0.052+0.225× gestational age; thickness (mm)=-0.174+0.085× gestational age. The dimension-gestational age correlation coefficients were: r=0.779 for length, r=0.676 for width and r=0.494 for thickness; these were statistically significant (P<0.01). The maximum increase in thickness and width of the corpus callosum occurred between 19 and 21 weeks' gestation, while its length followed a constant growth rate. The normal mean length, width and thickness of the corpus callosum per week, and the 95% confidence limits, were defined. Conclusions: The present study offers normative measurements of the fetal corpus callosum and may facilitate a more objective diagnosis of its congenital abnormalities.