Scientists say pregnancy creates lasting changes in women’s brains that may help prepare them for motherhood. They published their findings in the journal Nature Neuroscience.

“Pregnancy involves radical hormone surges and biological adaptations,” the authors write. “However, the effects of pregnancy on the human brain are virtually unknown.”

To investigate these effects, neuroscientists recruited couples who were trying to conceive for the first time and gave them brain scans. Some of the couples became parents and some did not, which created a sort of built-in control group. Once the babies were born, the researchers scanned participants’ brains; two years later, they did it again.

The scans revealed a clear difference between the two groups. New moms’ brains were missing something: a substantial amount of gray matter in the region associated with socialization. The disparity between the two groups’ brains were so significant that the researchers could spot which women had been pregnant just by looking at their scans.

But far from being a problem, the researchers say, this reduction in gray matter may actually be the brain’s way of paving the way for a strong mother-child relationship. The researchers found no memory loss or other cognitive problems. In other words, the gray matter loss isn’t brain damage. It’s tidying up in preparation for the challenging new cognitive work of motherhood.

To confirm this idea, the scientists gave the new moms another round of brain scans, this time while the women looked at pictures of their babies and babies they’d never seen before. Sure enough, the tidied-up portions of the women’s brains were especially active as they gazed on their own offspring. The more gray matter lost, the stronger the connection.

Two years after giving birth, new moms’ brains were still lighter on gray matter in that region than they had been before they became pregnant.

Co-author Oscar Vilarroya is a neuroscientist at the Universitat Autònoma de Barcelona in Spain. “The findings point to an adaptive process related to the benefits of better detecting the needs of the child, such as identifying the newborn's emotional state,” he said in a statement. “Moreover, they provide primary clues regarding the neural basis of motherhood, perinatal mental health and brain plasticity in general."