Maternal Brain Gray Matter Volume Increases Postpartum, Linked to GABAA, Glutamate, and Hormone Receptors

The profound hormonal shifts and experiences of pregnancy and childbirth are known to induce significant, yet poorly understood, changes in the maternal brain. A critical gap exists in characterizing the long-term neurobiological adaptations that underpin maternal brain plasticity and postpartum mood regulation. Understanding these dynamic changes, particularly how they relate to neurotransmitter and hormone receptor systems, is crucial for identifying potential biomarkers or therapeutic targets for postpartum mood disorders and supporting maternal well-being.

Researchers longitudinally monitored 24 postpartum women across six time points over the first 24 weeks following childbirth. Using structural MRI, they investigated changes in voxel-wise gray matter volumes (GMV) over time and compared them to nulliparous women. The study aimed to associate these volumetric changes with known distributions of GABAA, glutamate, cortisol, estradiol, progesterone, and oxytocin receptors, providing insights into the underlying neurochemical mechanisms.

Maternal gray matter volumes (GMV) continued to increase for at least 24 postpartum weeks, although the rate appeared to slow towards later time points. From the outset, these GMV changes showed a significant association with GABAA and glutamate receptor distributions, suggesting a role for the excitation-inhibition balance. The most pronounced increase was observed at three weeks postpartum compared to childbirth, with changes strongly co-localizing with cortisol, estradiol, and progesterone receptor systems. Later in the postpartum phase, specifically from 12 to 24 weeks, the volumetric increase co-localized with areas of higher oxytocin receptor density. Compared to nulliparous controls, maternal brains exhibited persistently smaller GMV in the amygdala, hippocampus, putamen, and SMA across the entire observation period. In the later postpartum phase, smaller volumes in the left hippocampus, parahippocampal gyrus, and amygdala were linked to reduced hostility toward the infant. > The sustained, receptor-specific brain adaptation throughout the postpartum period was complemented by the experience of maternity, likely mediated by oxytocin release, indicating a possible role of the excitation-inhibition balance in postpartum mood regulation.