Pregnancy changes a mother's brain for years, study shows
12/31/2016, 6 a.m.
(CNN) Women expect the physical changes of pregnancy, yet having a baby also produces some changes in the brain.
Pregnancy alters the size and structure of brain regions involved in understanding the thoughts, feelings, beliefs and intentions of others, according to a study published Monday in the journal Nature Neuroscience.
Mothers with the greatest degree of overall brain change scored higher than others when tested on the strength of their maternal bonds, the researchers discovered. Many of the changes lasted two years after giving birth.
"We haven't investigated whether these changes stretch beyond this period," said Elseline Hoekzema, co-lead author of the study and a senior brain scientist at Leiden University in the Netherlands.
In rodents it is known that some of the changes in brain and behavior following a pregnancy last until old age, Hoekzema noted. In humans, it's not clear -- Hoekzema followed the participants in her own human study for two years only.
Because of the new study's short timeframe, how long lasting these changes may be in women remains unknown, said Dr. Rodney L. Wright, associate professor of clinical obstetrics & gynecology and women's health at Albert Einstein College of Medicine.
"The significance of these changes and the duration of these changes is yet to be determined," said Wright, who was not involved in this research.
Increasing social awareness
Hoekzema and Erika Barba-Müller, co-lead author and a psychologist, began the study while working together at Autonomous University of Barcelona.
Pre-conception, 25 women who became mothers for the first time and 19 of their male partners underwent high resolution MRI brain scans. After completing their pregnancies, these same participants were re-scanned. For comparison, 20 women who had never given birth and 17 of their male partners were also scanned at the same time intervals.
The new mothers showed a loss of gray matter in several brain areas associated with social cognition, a form of emotional intelligence.
While changes to the brain were clear, how to interpret them is not.
"Loss of volume does not necessarily translate to loss of function," said Hoekzema, "Sometimes less is more." She explained that the loss of gray matter could "represent a fine-tuning of synapses into more efficient neural networks."
Our teen-aged brains undergo a similar process of "synaptic pruning," explained Hoekzema. At that developmental period, weaker brain connections are eliminated, leaving a more efficient and more specialized neural network, she said. Adolescents with a more "mature" network -- meaning, less grey matter -- actually show increased brain activity in their thinned-down regions, she observed. "Reduced volume does not necessarily reflect reduced brain activity," said Hoekzema.
In fact, participants of the new study took cognitive tests during their MRI session with no significant changes seen over time. However, following their pregnancies, the mothers had fewer correct responses on the verbal word list learning task, though to an extent considered insignificant by the researchers.
Reduction in gray matter occurred in various regions of the brains of pregnant women, including the prefrontal and temporal cortex.