A Longitudinal Study of Children's Hippocampal Development: Investigating Maternal Physical Activity, Depression, and Education

The developing hippocampus is particularly sensitive to early environmental influences, including during pregnancy. This longitudinal neuroimaging study examined associations between prenatal maternal physical activity and depression, maternal education, and hippocampal development from early childhood to early adolescence. Participants were mothers and their 113 children (59 females; mean age 4.16 ± 1.25 years at first scan) with 510 magnetic resonance imaging scans. Maternal physical activity and depressive symptoms were assessed during the second trimester. Hippocampal diffusion metrics-including fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD)-as well as volume were measured. Developmental trajectories were analyzed with generalized fractional polynomial mixed models. Results showed significant age-related changes in hippocampal volume and diffusivity, with sex differences in FA development. Bilateral hippocampal volume increased nonlinearly with age, and FA, MD, and RD changed in line with typical brain maturation patterns. However, in contrast to our pre-registered hypotheses, prenatal maternal physical activity was not significantly associated with hippocampal structure. Additionally, in exploratory analyses, we found no significant associations between maternal education or prenatal maternal depression and hippocampal structure. These findings provide a comprehensive characterization of hippocampal development from childhood to adolescence and suggest that prenatal maternal physical activity, depression, and education are not strongly related to hippocampal structure. This work underscores the value of longitudinal neuroimaging and flexible modeling approaches in understanding early brain development.