To evaluate the clinical value of prenatal three-dimensional (3D) inversion imaging of the sylvian fissure, parietal occipital sulcus, and calcarine sulcus.

The sylvian fissure, parietal occipital sulcus, and calcarine sulcus were assessed prospectively by 3D ultrasound (3D-US) inversion imaging and two-dimensional ultrasound (2D-US) in 133 fetuses with no structural abnormalities between 19 and 36⁺⁶ weeks of gestation at Shenzhen Maternity and Child Healthcare Hospital from June 2019 to July 2020. The examinations were divided into six groups according to gestational age. For each group, these sulci were assessed as absent or present. The changes of these 3D sulci imaging were observed in different groups. Thirty fetuses were randomly selected for intra- and inter-observer reproducibility testing by pearson chi-square test.

Along with the increase of the gestation age in different groups, the rates of 2D and 3D examinations to display the structures both became higher and higher. 2D-US and 3D-US showed 100% of sylvian fissure, parietal occipital sulcus, and calcarine sulcus at 22, 23, and 24~36 weeks, respectively. The display rate had no statistical difference between 2D-US and 3D inverted ultrasound in the six groups (P＞0.05). However, 3D inversion ultrasound was more vivid and intuitive than 2D-US. No significant intra- and inter-observer variability was found.

3D inversion imaging can be used to better observe the morphological and spatial changes of the sylvian fissure, parietal occipital sulcus, and calcarine sulcus during middle and late pregnancy, which is an intuitive supplementary means for prenatal evaluation of cerebral cortex development and provides a new idea for future teaching and research of cerebral cortex development.