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 Many of these changes appeared to last at least two years after
giving birth, the study found. Mothers who had the most pronounced
alterations in their brains also scored higher on tests of emotional
attachment to their babies than women whose brains underwent subtler
changes.
“This study provides the first insights into the impact of pregnancy
on the gray matter architecture of the human brain,” said lead study
author Elseline Hoekzema of the University of Leiden in The
Netherlands.
While the exact cause of these shifts in the brain isn’t clear, it’s
possible the changes may help women prepare for the social demands
of motherhood, researchers report in the journal Nature
Neuroscience.
For the study, researchers scanned the brains of 25 women who had
never had babies, then did imaging tests again after the women gave
birth for the first time.
Researchers also looked at brain scans from 19 first-time fathers,
17 men without children and 20 women who had never given birth.
Compared to the other participants, the first-time mothers had a
distinct loss of gray matter in regions of the brain associated with
what’s known as “theory of mind,” or the ability to attribute mental
states such as thoughts, feelings and intents to themselves and
other people.
When researchers showed these first-time mothers pictures of their
own babies, they had more activity in some of these
pregnancy-altered brain regions than when they looked at images of
other babies, the study also found.
Nearly all of the gray matter changes were still present in scans
done two years after women delivered their babies. Some of the gray
matter volume that was reduced during pregnancy returned in the
hippocampus, a region associated with memory.
This pattern of structural changes was so consistent that it could
be used to distinguish the brains of women who had given birth from
those who had not, as well as to predict the quality of mothers’
attachment to their infants in the postpartum period, the
researchers conclude.
Beyond its small size, limitations of the study include the lack of
information about when or why changes in the brain might occur for
first-time mothers.
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It’s unclear if the changes in the mothers’ brains were caused by
nine months of pregnancy, many hours of labor and delivery or by the
first days and weeks of mother-infant bonding, said Dr. Rebecca Saxe,
a neuroscience researcher at the Massachusetts Institute of
Technology in Cambridge who wasn’t involved in the study.
The study also doesn’t tell us what happens in subsequent
pregnancies, Saxe added by email.
“This could be a once in a lifetime change, even if you have many
more pregnancies,” Saxe said. “If so, we should be especially
careful about making overly strong inferences about the link between
neural changes and parent-infant bonding - since obviously, mothers
do bond with later children.”
Still, the findings add to a growing body of research documenting
shifts in the brain associated with pregnancy and parenthood, said
Dr. Mel Rutherford, a psychology researcher at McMaster University
in Hamilton, Ontario, who wasn’t involved in the study.
Other research has found women may become more vigilant about
strangers and develop a nesting instinct during pregnancy, both of
which may be linked to changes in the brain, Rutherford said by
email.
“More generally, there is evidence of broader cognitive
reorganization: Some cognitive processes become prioritized during
the pregnancy, perhaps in service of protecting the investment in
the pregnancy,” Rutherford said.
SOURCE: http://go.nature.com/2h2vQMu Nature Neuroscience, online
December 19, 2016.
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