Assessment of length and area of corpus callosum by three-dimensional ultrasonography - Revista Brasileira de Ginecologia e Obstetrícia

PURPOSE: to establish reference values for the length and area of the fetal corpus callosum between the 20th and 33rd weeks of gestation using three-dimensional ultrasound (3DUS). METHODS: this cross-sectional study involved 70 normal pregnancies with gestational age between 20 and 33 weeks. An Accuvix XQ instrument with a convex volumetric transducer (3 to 5 MHz) was used. To assess the corpus callosum, a transfrontal plane was obtained using the metopic suture as an acoustic window. Length was obtained by measuring the distance between the proximal and distal extremities of the corpus callosum. Area was obtained by manual tracing of the external corpus callosum surface. The means, medians, standard deviations, and maximum and minimum values were calculated for the corpus callosum length and area. Scatter graphs were created to analyze the correlation between corpus callosum length and area and gestational age and biparietal diameter, the quality adjustments was verified according to the determination coefficient (R²). The intraclass correlation coefficient (ICC) was used to assess the intraobserver variability. RESULTS: mean corpus callosum length increased from 21.7 (18.6 – 25.2 mm) to 38.7 mm (32.6 – 43.3 mm) between 20 and 33 weeks of pregnancy, respectively. Mean corpus callosum area increased from 55.2 (41.0 – 80.0 mm²) to 142.2 mm² (114.0 – 160.0 mm²), between 20 to 33 weeks of pregnancy, respectively. There was a strong correlation between corpus callosum length and area and gestational age (R² = 0.7 and 0.7, respectively) and biparietal diameter (R² = 0.7 and 0.6, respectively). Intraobserver variability was appropriate, with an ICC of 0.9 and 0.9 for length and area, respectively. CONCLUSIONS: reference values for corpus callosum length and area were established for fetuses between 20 and 33 weeks gestation. Intraobserver variability was appropriate.