Pregnancy completely rewires mothers’ brains — study

We know that pregnancy completely changes a mother’s body, but new research shows changes in the brain are just as dramatic.
Based on brain scans of one healthy 38-year-old woman’s brain over two years, scientists have created the first comprehensive map of how the brain changes during pregnancy.
The data, published in the journal Nature Neuroscience, found a dynamic reorganization in the mother’s brain — the changes unfolded like clockwork over the course of the pregnancy.
Almost all parts of the brain showed changes in function and anatomy, including in regions involved in social and emotional processing — some of which lasted for two years after the baby was born.
While the research focused on one woman’s pregnancy, the work joins a small body of research showing that the process of being a mother, called matrescence, is another stage of development.
Scientists are beginning to discover how hormonal changes during pregnancy and motherhood overhaul the brain’s anatomy and function, as they also do during adolescence and menopause.
“It seems like the human brain goes through this choreographed change across gestation, and we were finally able to observe the change in real time,” said lead author Emily Jacobs of the University of California, Santa Barbara, US.
The brain studied is that of Elizabeth Chrastil, who is also a neuroscientist at the University of California, Irvine. The researchers imaged Chrastil’s brain using magnetic resonance imaging (MRI) every few weeks, starting before the pregnancy and continuing for two years after the birth.
“This was an intense undertaking. We did 26 scans before,” said Chrastil in a media statement with Jacobs.
The researchers found sweeping changes in overall brain neuroanatomy which unfolded week by week during the pregnancy.
Inside Chrastil’s brain, grey matter volume, cortical thickness, white matter microstructure, and ventricle volume all changed.
“The findings are remarkable. It shows that in a relatively short time, pregnancy can alter the brain as much as other life stages, like adolescence,” said neuroscientist Clare McCormack of New York University Langone Health, US, who was not involved in the study.
Some of Chrastil’s brain’s white matter tracts also grew stronger in the second trimester. White matter are the information-sending tracts between brain regions. Stronger white matter tracts means information is being carried more efficiently.
The changes were all over the brain too — “over 80% of my brain regions showed reductions in grey matter volume,” Chrastil said.
Grey matter is brain tissue with high concentrations of neuron cell bodies, where information is processed. Reductions in grey matter volume are sometimes associated with reduced memory and cognitive function.
However, the study authors say a reduction in grey matter during pregnancy isn’t necessarily a bad thing. It’s more like a wave of brain refinement as the brain prepares for motherhood — like the process of chiseling a block of marble into a sculpture.
“This change probably reflects the fine tuning of neural circuits. This adaptive process enables the brain to become more specialized,” said Jacobs.
The changes in Chrastil’s brain were linked with shifts in hormone levels of estrogen and progesterone during the pregnancy.
But the study doesn’t yet tell us how, or whether, these anatomical changes alter a mother’s psychology or health: Which types of brain restructuring cause mood changes or sleep disturbances during pregnancy? Which changes create the powerful bonds of motherly love? Scientists don’t yet know.
Future research in many more women is now underway to determine how these brain changes impact a mother’s psychology and health.
The insights could improve understanding of conditions such as postnatal depression and preeclampsia, a form of high blood pressure during pregnancy.
“This study is an important step towards improving understanding and treatment of perinatal mood and anxiety disorders, which affect as many as 1 in 5 women who give birth,” McCormack told DW.
But ultimately this study opens up more questions than it answers, said Chrastil: “We’re only just starting to scratch the surface of understanding the brain during pregnancy.”
There are so many unanswered questions because of the “shocking” fact that this is the first study to consistently map brain changes during pregnancy, write the study authors in their paper.
“It’s 2024 and this is the first glimpse we have of this fascinating neurological transition. There is so much about the neurobiology of pregnancy we don’t understand yet. It’s a biproduct of the fact that biosciences have historically ignored women’s health,” said Jacobs.
Of the 50,000 brain imaging articles published in the last thirty years, less than one in a hundred focused on health factors unique to women, like pregnancy, Jacobs highlighted in a press statement.
“Male/female differences in brain function have not traditionally been appreciated by most neuroscientists or clinicians,” said Diana Krause, a hormone expert at the University of California, Irvine, US, who was not involved in the study.
“Why? As a woman scientist it makes no sense to me, but clearly, sex and hormones have a tremendous impact, and it is great to see more work focusing on these issues,” Krause told DW.
The new study kicks off the Maternal Brain Project, an international effort to understand the impact of pregnancy on maternal brain function. Larger cohorts of women and their partners are being enrolled for studies in the US and Spain.
Edited by: Zulfikar Abbany
Primary source:
Neuroanatomical changes observed over the course of a human pregnancy. Published by Pritschet, L., Taylor, C.M., Cossio, D. et al. in Nature Neuroscience (September 2024). https://doi.org/10.1038/s41593-024-01741-0