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Many of us have heard the term “pregnancy brain” used to describe the way a woman’s thinking may be altered while she is pregnant. But is this a myth or a scientific truth? It turns out brain remodelling does occur during pregnancy, and it can last at least two years after birth.

Neuroscientist Elseline Hoekzema of Leiden University led a study in which a research team at Autonomous University of Barcelona performed brain scans on first-time mothers before and after pregnancy. The researchers found significant changes in gray matter in brain regions associated with theory of mind and social cognition. These regions were also activated when they looked at photos of their infants. The changes predicted the women’s scores on a test of maternal attachment. In fact, these changes were so clear that a computer algorithm could use them to pick out which women had been pregnant. The changes were still present two years after birth.

While pregnant, a woman experiences an increase in sex steroid hormones like estrogen and progesterone in order to help her prepare for carrying a child. The only other time the body produces this many hormones is during puberty. According to previous research, these hormones produced during puberty lead to dramatic structural and organizational chances in the brain. Both boys and girls lose gray matter throughout adolescence as their brains are sculpted into their adult form. While a lot of research has focused on this phenomenon, there has been a marked lack of research focusing on brain changes in pregnant women.

In Hoekzema’s study, anatomical brain scans were performed on a group of women who were trying to get pregnant for the first time. 25 of the women got pregnant, and they were rescanned soon after they gave birth. 11 of them were scanned two years after that. The research also scanned men and women who weren’t trying to have a child as well as first-time fathers for comparison. A standard scale was used to rate the attachment between mother and infant.

The loss of gray matter that occurs in brain regions involved in social cognition is not necessarily a bad thing. These regions had the strongest response when mothers looked at photos of their infants. Gray matter loss was not seen in new fathers or nonparents.

No one is completely sure why women lose gray matter during pregnancy. Hoekzema theorizes that this may be because their brains are becoming specialized in ways that will make them more suited for motherhood and able to respond to the needs of their babies. The recent study focused on documenting brain changes during pregnancy, but Hoekzema hopes to do follow-up work in order to figure out how brain changes relate to postpartum depression or attachment issues between mothers and children.

This study is significant for a number of reasons. Ronald Dahl, a neuroscientist at the University of California, Berkeley, is excited about the fact that this study offers evidence that suggests these changes are adaptive. An evolutionary psychologist at McMaster University in Ontario named Mel Rutherford is excited that the study is the first one to his knowledge that uses neuroimaging to track brain changes during pregnancy. No matter how you look at it, this is a revolutionary study that will change the way we study brain evolution during pregnancy in the future.