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

Objective To establish reference ranges during human pregnancy for normal f etal corpus callosum dimensions. Design In a prospective, cross-sectional study of 258 fetuses between 16 an d 37 weeks of gestation, measurements of the length, width, and thickness a t 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 th e corpus callosum were 5.6 (standard deviation, 1.6; 95% confidence interva l, 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 functio n 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 a ge; thickness (mm) = -0.174 + 0.085 x gestational age. The dimension-gestat ional age correlation coefficients were: r = 0.779 for length, r = 0.676 fo r width and r = 0.494 for thickness; these were statistically significant ( P < 0.01). The maximum increase in thickness and width of the corpus callos um occurred between 19 and 21 weeks' gestation, while its length followed a constant growth rate. The normal mean length, width and thickness of the c orpus callosum per week, and the 95% confidence limits, were defined. Conclusions The present study offers normative measurements of the fetal co rpus callosum and may facilitate a more objective diagnosis of its congenit al abnormalities.