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 midbody 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) min. 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) min, respectively. The size of the corpus callosum as a function of gestational age was expressed by regression equations: length (mm) = -20.40 + 1.92 x gestational age, width (mm) = -0.052 + 0.225 x gestational age; thickness (mm) = -0.174 + 0.085 x 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.