Reference ranges for fetal brain fissure development on 3-dimensional sonography in the multiplanar mode.

OBJECTIVES To determine reference ranges for measurements of fetal cerebral fissures by 3-dimensional (3D) sonography in the multiplanar mode and to evaluate the reliability and concordance of these measurements. METHODS A cross-sectional study was conducted on 393 women with normal pregnancies at 22 weeks to 33 weeks 6 days. The distances between the internal bone plate of the fetal calvaria and the sylvian, parieto-occipital, hippocampal, and calcarine fissures were assessed. To obtain the distances for the first 3 fissures, a 3D sweep was made in the axial plane, at the level of the lateral ventricles. To obtain the distance for the calcarine fissure, a coronal sweep was used, at the level of the occipital lobes. To evaluate the correlation between the fissures and gestational age, polynomial regression was performed with adjustments using the coefficient of determination (R(2)). Reliability was determined with intraclass correlation coefficients and concordance with concordance limits. RESULTS The mean distances ± SD to the sylvian, parieto-occipital, hippocampal, and calcarine fissures were 10.42 ± 2.28, 22.38 ± 3.23, 24.88 ± 4.67, and 21.19 ± 2.73 mm, respectively. These distances correlated with gestational age such that the best fit with the linear equation produced R(2) values of 0.582, 0.627, 0.860, and 0.458 for the sylvian, parieto-occipital, hippocampal, and calcarine fissures. Reliability analyses showed intraobserver and interobserver intraclass correlation coefficients of 0.90 to 0.95 and 0.85 to 0.97. The concordance limits were-1.33 to 1.30 and -2.38 to 2.28 mm for the intraobserver evaluation and -1.60 to 2.57 and -3.51 to 2.73 mm for the interobserver evaluation. CONCLUSIONS Cerebral fissures can be measured by 3D sonography at 22 to 33 weeks of pregnancy with acceptable reliability and concordance. Reference ranges for this gestational period have thus been described.