Pregnancy shrinks cortical gray matter then partially rebounds, recovery tied to bonding

A study led by the Autonomous University of Barcelona and published in Nature Communications found that cortical gray matter volume and cortical thickness fall during pregnancy and then partially rebound in the first year after birth, with stronger postpartum recovery associated with closer maternal‑infant bonding at six months.

The research, coordinated by Òscar Vilarroya and Susana Carmona and with first authors Camila Servin‑Barthet and Magdalena Martínez‑García, used neuroimaging to chart brain changes during pregnancy for the first time in a cohort described by researchers as larger and more carefully controlled than many prior reports. The project received a 972,414 euro grant from the la Caixa Foundation.

Imaging showed that total gray matter volume and cortical thickness decreased across most of the cerebral cortex and in several deep brain areas throughout pregnancy. The reductions were “much larger than the variability seen in non‑pregnant women over a similar period,” the authors report, and were accompanied early in gestation by increased white matter organization that returned to baseline after birth. The study also reports that gray matter volumes partially rebounded postpartum and that recovery appears to continue beyond the first postpartum year.

Hormonal shifts tracked during pregnancy were correlated with these brain changes: fluctuations in the steroid metabolites estriol‑3‑sulfate and estrone‑sulfate aligned with the observed gray matter trajectory. The investigators also measured functional network organization and neural metabolites, and the Nature Communications paper assessed how a second pregnancy uniquely altered gray matter structure, network organization and white matter tracts.

Crucially for families and clinicians, the study linked brain recovery to behavior. Women who showed a higher percentage of gray matter volume recovery during the postpartum period reported greater bonding with their infant at six months, and maternal psychological well‑being strengthened that association. The authors and other scientists have urged a shift in public framing away from simplistic tropes: "It is time to move beyond the 'baby brain' cliche, say scientists who scanned dozens of women's brains."

The new work sits amid a patchwork of earlier findings. Longitudinal studies such as Hoekzema et al. reported postpartum reductions in specific cortical regions that persisted for two years, while other analyses found larger gray matter volumes decades after pregnancy or reported widespread gray‑matter gains after giving birth. Researchers reviewing these divergences note that differences in study design — in‑pregnancy repeated scanning, pre/post snapshots and decades‑after cross‑sectional analyses — cohort age and social or selection factors may explain inconsistent results.

The authors and collaborators emphasize the study fills a key gap in maternal neuroscience by measuring the gestational window directly. "We wanted to look at the trajectory of brain changes specifically within the gestational window," said Laura Pritschet, whose separate repeated‑scan work complements this cohort approach, adding that "our goal was to fill the gap and understand the neurobiological changes that happen during pregnancy itself."

Clinically, investigators see implications for maternal mental health but stop short of immediate practice changes. "There are now FDA‑approved treatments for postpartum depression... but early detection remains elusive. The more we learn about the maternal brain, the better chance we'll have to provide relief," Pritschet has said. Teams now plan to follow larger, more diverse samples and to combine neuroscience with reproductive immunology, proteomics and AI to determine which variations in the pregnancy brain predict outcomes such as postpartum depression and which findings generalize across populations.