The expectant brain: Being pregnant causes changes in brain morphology in the early postpartum period

There is growing evidence that pregnancy may have a significant impact on the maternal brain, causing changes in its structure. However, the patterns of these changes have not yet been systematically investigated. Using voxel-based (VBM) and surface-based morphometry (SBM), we compared a group of healthy primiparous women (n = 40) with healthy multiparous mothers (n = 37) as well as nulliparous women (n = 40). Compared to the nulliparous women, the young mothers showed decreases in gray matter volume in the bilateral hippocampus/amygdala, the orbitofrontal cortex/subgenual prefrontal area, the right superior temporal gyrus, the right insula, and the cerebellum. However, these pregnancy-related changes in brain structure did not predict the quality of mother-infant attachment at either 3 or 12 weeks postpartum, nor were they more pronounced among the multiparous women. SBM analyses showed significant cortical thinning especially in the frontal and parietal cortices, with the parietal cortical thinning likely potentiated by multiple pregnancies. We conclude, therefore, that the widespread morphological changes seen in the brain shortly after childbirth reflect substantial neuroplasticity. Also, the experience of pregnancy alone may not be the underlying cause of the adaptations for mothering and caregiving. As regards the exact biological function of the changes in brain morphology as well as the long-term effect of pregnancy on the maternal brain, further longitudinal research with larger cohorts will be needed to draw any definitive conclusions. Significance StatementBiological adaptations during pregnancy affect the maternal brain. Here, we evaluated morphological changes in the brain of mentally healthy young mothers within the first four days of childbirth. Compared to the nulliparous women, the young primiparous and multiparous mothers demonstrated a substantial reduction in gray matter volume in brain areas related to socio-cognitive and emotional processes. Cortical alterations due to pregnancy-related adaptations are not the underlying cause of mother-infant attachment.