Spatiotemporal atlas of the fetal brain depicts cortical developmental gradient in Chinese population

The fetal brains experience rapid and complex development in utero during the second and third trimesters. MRI atlas of the fetal brain in this period enables us to quantify the normal fetal brain development in the spatiotemporal domain. In this study, we constructed a high quality spatiotemporal atlas between 23-38 weeks gestational age (GA) from 90 healthy Chinese fetuses using a pairwise and groupwise registration-based pipeline. We quantified the fetal cortical morphology and characterized the developmental trajectories of each morphological index. The cortical thickness exhibited a biphasic growth pattern; the developmental trend of curvature fitted well into the Gompertz model; sulcal depth increased linearly while surface area expanded exponentially. The cortical thickness and curvature trajectories consistently pointed to a characteristic time-point during development around 31 weeks of GA. The characteristic GA and growth rate obtained from individual cortical regions suggested a central-to-peripheral developmental gradient, with the earliest development in the parietal lobe, and we also observed within-lobe regional orders, which may be linked to biophysical events such as dendritic arborization and thalamocortical fibers ingrowth. The proposed atlas was also compared with an existing fetal atlas from a Caucasian/mixed population. Finally, we examined the structural asymmetry of the fetal brains and found extensive asymmetry that dynamically changed with development. The current study depicted a comprehensive profile of fetal cortical development and the established atlas could be used as a normative reference for neurodevelopmental and diagnostic purposes, especially in the Chinese population.