How Pregnancy Changes Women’s Brains to Prepare Them for Motherhood

The study, which was published in the journalNature Neuroscience, found that pregnancy creates long-term changes in brain structure. Over the course of over five years, researchers at the Universitat Autonoma de Barcelona in Spain performed brain scans on women before and after their first pregnancies. When compared with three control groups—women who had never been pregnant, first-time fathers, and men without children—the results were striking: In new mothers, there were "pronounced and long-lasting" reductions in grey matter in regions associated with social cognition, or how one conceives of one's own mental state and the mental states of others.

The changes were so clear, according to the study, that researchers were able to tell which women had been pregnant based on the changes in grey matter volume alone. "I was somewhat surprised by the wonderful consistency of the findings. This is something you hardly ever see in neuroimaging research," Elseline Hoekzema, one of the study's co-authors, told Broadly. "I had never seen anything like this in terms of strength and consistency."

The study speculates that the change in grey matter indicates a heightened ability to process social information, "including enhanced emotion and facial recognition." This could serve various potential purposes: making a mother more receptive to her child's needs, helping her perceive specific threats to her child, or simply promoting mother-infant bonding.

The idea of losing brain volume might seem worrying, but Hoekzema assured the New York Times that concluding that "pregnancy makes you lose your brain" would be incorrect. "Grey matter volume loss does not necessarily represent a bad thing," she said. "It can also represent a beneficial process of maturation or specialization." Indeed, researchers didn't observe any significant change in the new mothers' performance on cognitive tests when compared to the control group.

Hoekzema notes that there's still a great deal of work to be done in order to determine exactly what the changes in volume mean. "In humans, we cannot examine the brain in the same microscopic way you can do in animal studies," Hoekzema cautions. "Providing hard proof for an actual evolutionarily-driven purpose to the observed changes will always be difficult and will remain a matter of interpretation."

Still, researchers hope to determine the direct hormonal reason for the changes, hoping to potentially understand how they are possibly linked to changes in specific pregnancy hormones.

"It's a bit early to draw any strong conclusions regarding our pregnancy and motherhood," Hoekzema told Broadly. "This is only the first study to show that these changes exist."