To explore sulcus and gyrus alterations on normal fetal brain surface using three-dimensional inverse crystal and realistic vue (3D-ICRV) technique.

This is an retrospective study in which we retrospectively reviewed the 3D volume images of the normal fetal brain (15 to 35 gestational weeks) collected from January 2019 to December 2021 at Shenzhen Maternity and Child Healthcare Hospital Affiliated to Nanfang Medical University. 3D volume images were acquired in the transthalamic or transventricular plane on transabdominal ultrasonography and post-processed by 3D-ICRV. Volume images that were able to demonstrate the primary sulci and gyri on fetal brain surface clearly were selected. The morphology of the sulcus and gyrus and the alteration of apical angle on the Sylvian fissure were recorded according to the order of gestational weeks. Postnatal follow-up was performed in all cases.

During the study period, 300 ultrasound examinations were reviewed, and 588 3D volume images from 294 fetuses (n=294; median gestational weeks, 26.93; median maternal age, 31.22 years) were qualified. The Sylvian fissure was the first structure recognized between 15 to 25 gestational weeks. From 26 to 35 gestational weeks, the primary sulci and gyri emerged gradually. At 26 weeks, the central sulcus and superior temporal sulcus appear first, and then the superior frontal sulcus, intraparietal sulcus, inferior frontal sulcus and inferior temporal sulcus appear successively. Gestational weeks of 25 to 30 was the best time window to visualize the primary sulcus and gyrus on brain surface. Follow-up showed no abnormality.

Fetal brain surface configuration can be visualized through 3D-ICRV. Understanding these changes is of great significance in evaluating the maturity of cerebral cortex development as well as prenatal consultation and further examination for clinical management.