Pregnancy Induces Transformative Changes in 94% of Maternal Grey Matter

A study led by the UAB has analysed the brains of women during pregnancy for the first time using neuroimaging techniques. The study included non-pregnant mothers, whose partners were pregnant, to distinguish biological effects from those caused by the experience of being a mother. The research shows that there is a reduction and partial recovery of almost 5% of grey matter in 94% of the total grey matter volume of the brain, especially in regions linked to social cognition.
Researchers from the Universitat Autònoma de Barcelona (UAB), the Gregorio Marañón Health Research Institute and the Hospital del Mar Research Institute, together with other prestigious international institutions, have published the first longitudinal neuroimaging (Magnetic Resonance Imaging) study in a cohort of more than a hundred women seeking to become mothers for the first time. The findings reveal a dynamic trajectory in the brain during pregnancy and postpartum, significantly linked to the steroid hormone fluctuations inherent to pregnancy, and to the psychological well-being of the mothers. The article, led by Camila Servin-Barthet and Magdalena Martínez-García as first authors and coordinated by Òscar Vilarroya and Susana Carmona, has been recently published in the prestigious journal Nature Communications. This study, which received a grant of 972,414 euros from the ”la Caixa” Foundation to be carried out, represents a crucial advance in maternal brain research.
In total, the researchers have analyzed the brain of 179 women to study the structural changes that occur during the second and third trimester of pregnancy and the first six months postpartum, using a scan taken before conception as a baseline. For the first time, this cohort includes a group of non-gestational mothers as a control group: women whose partners underwent pregnancy during the study. The inclusion of this group of women made it possible to determine that the trajectory of brain changes is mainly attributed to the biological process of pregnancy, rather than to the experience of becoming a mother.
This work has revealed that, during the first pregnancy, gray matter volume in the brain is reduced by up to 4.9%, with a partial recovery during the postpartum period. These changes are observed in 94% of the brain, being particularly prominent in regions linked to social cognition. The study also demonstrates, for the first time, that the evolution of these morphological changes in the brain is associated with fluctuations in two estrogens (estriol-3-sulfate and estrone-sulfate), hormones that increase exponentially during pregnancy and return to basal levels after delivery. Specifically, the researchers observed that a greater increase and subsequent decrease in estrogen levels is associated with a greater decrease and subsequent recovery of brain gray matter volume.
Finally, in analyzing the possible influence of brain changes on maternal behavior, this study discovered that women with a higher percentage of gray matter volume recovery during postpartum reported a greater bond with their infant at 6 months postpartum, and that maternal well-being is a key factor that positively enhances the association between brain changes and maternal-filial bonding.
This study, which comprehensively characterizes normative brain changes during pregnancy and postpartum, stands out for both its sample size and rigorous methodological control, including carefully selected groups that allowed the distinguishing of pregnancy-specific changes from those linked to the experience of motherhood. The data obtained not only establishes a key reference for understanding the neurobiology of the maternal brain, but also serves as a basis for future studies analyzing other neuroimaging modalities and more diverse samples, including women with clinical conditions such as postpartum depression, allowing progress towards a more complete and applied understanding of the brain in this vital period.