Reference ranges of fetal cisterna magna length and area measurements by 3-dimensional ultrasonography using the multiplanar mode.

This study aimed to establish reference values for the length and area of the fetal cisterna magna using the multiplanar mode of 3-dimensional ultrasonography. A cross-sectional study including 224 normal pregnant women between 17 weeks 0 days and 29 weeks 6 days of gestation was carried out. The area and length of the fetal cisterna magna were measured in the axial plane at the level of the cerebellar transverse diameter. Reliability was determined by intraclass correlation coefficient. The mean length and area of the fetal cisterna magna ranged from 0.50 ± 0.10 to 0.79 ± 0.18 cm and 0.95 ± 0.18 to 3.09 ± 0.62 cm(2), respectively. Intraobserver reliability for the length and area (intraclass coefficients: 0.86 and 0.91, respectively) and interobserver reliability (intraclass coefficients: 0.64 and 0.82, respectively) were good. Three-dimensional ultrasonography using the multiplanar mode is a reliable method for the determination of reference values for the length and area of the fetal cisterna magna.