‘Baby brain' is real. 3 things to know about what's happening to your brain

CTV News

21-05-2025

Pregnancy is one of the three Ps (puberty, pregnancy and perimenopause), a time when a person's brain undergoes physical changes due to hormones. d3sign//File via CNN Newsource
Science has pretty well established that the brain isn't static; it changes and adapts throughout our lives in response to life events in a process called neuroplasticity.
Researchers are discovering this is especially true of female brains, which get remodeled significantly during the three Ps: puberty (as do the brains of adolescent males), pregnancy and perimenopause.
All three transitions are a frequent butt of pop-culture jokes: the sulky, risk-taking teenager who only wants to be with friends; the scattered mom-to-be who leaves her cell phone in the fridge and can't remember where she parked the car; and the hormonal middle-aged woman who can't focus and spontaneously combusts with hot flashes.
But far from being laughable, these behavioral stereotypes are the external manifestations of big internal shifts, many of them linked to the effects of fluctuating hormones on the brain.
Cognitive neuroscientist Laura Pritschet, a postdoctoral fellow in the department of psychiatry at the University of Pennsylvania, is fascinated by how female hormones, including estrogen and progesterone, affect the brain's organization and functioning.
'The reason I chose that field is because I was a budding neuroscientist as an undergrad, interested in brain networks and obsessing over how intricate everything was in the brain to simply allow us to have a personality or remember things,' Pritschet told CNN Chief Medical Correspondent Dr. Sanjay Gupta recently, on his podcast Chasing Life.
'At the same time in my personal life, I was surrounded by menopausal women who were talking about their cognitive complaints and their attention issues,' she said. 'I thought we've got to connect these two together and understand this more.'
Pritschet even volunteered as a 'guinea pig' during graduate school, having her brain scanned and blood drawn for 30 days, across two complete reproductive cycles (both on and off birth control pills), to begin to answer the question of how the day-to-day fluctuations in hormones relate to the day-to-day changes in the brain.
Around this time, other researchers were studying what happens in the brain during pregnancy, Pritschet said, looking at the brain before and after gestation. They found many changes, but because the studies took a snapshot approach, many questions were left unanswered.
'If there's a 3 to 5% decrease in total gray matter volume, when is that occurring (during pregnancy), and how is it occurring?' Pritschet asked. 'We're missing huge gaps in what we call this metamorphosis.
'We know that the 40-week gestational window leads to these body adaptations to support the development of the fetus: We have increased plasma volume, immune function change, metabolic rate, oxygen consumption,' she said. 'What does this trajectory look like over gestation?'
To find out, Pritschet and her team tracked the brain changes in one woman, using MRI and blood draws, from pre-conception and fertility treatment throughout her pregnancy to two years postpartum. Their findings were published in the journal Nature Neuroscience in September.
'We saw this reduction in gray matter volume pretty much across the whole brain,' Pritschet explained. 'We saw increased white matter microstructure and ventricle size.' (Quick anatomy lesson: The brain is made up of gray and white matter. Gray matter is where most of the brain's thinking and processing takes place. White matter helps connect the different brain areas, allowing them to communicate with one another.)
'The inflection point was birth,' Pritschet said. 'We saw that those reductions persisted into postpartum, with slight recovery, meaning that certain areas of the brain showed this rise in gray matter volume in early postpartum. Others did not.'
Pritschet said this 'choreographed dance between major features of our brain' is in one respect a physical adaptation to the increased blood flow and swelling that comes with pregnancy.
Additionally, the changes may also be a preparation for the next stage: parenting.
'It's a fine-tuning of circuits,' she explained. 'We know that pregnancy is the lead-up to this time in your life where there's a lot of behavioral adaptation that has to occur, and new cognitive demands, and a new cognitive load.
'And so the idea here is that there is this pruning or this delicate rewiring to make certain networks or to make communication in the brain more efficient to meet the demands that are going to have to occur,' Pritschet said.
This theory is supported by earlier work. 'The first pinnacle papers that came out looking at neuroanatomy in human women from preconception to postpartum found that degree of change in gray matter volume — that sort of reduction — correlated with various … maternal behaviors (such as bonding). Again, that's all correlation,' she said.
'That's an area we need to do a lot more research on, and it needs a lot of context,' she said. 'But you can expect that if there's fine-tuning in these circuits that underlie cognitive or behavioral process, that the more fine-tuning it undergoes, the better performance you're going to have. That's the idea — but it's so much more complicated than that.'
What happens to the brain during pregnancy? Pritschet offers these three insights.
The only constant is change
The body is the outward sign of a lot of inner upheaval.
'Pregnancy is a transformative time in a person's life where the body undergoes rapid physiological adaptations to prepare for motherhood,' Pritschet said via email. 'But pregnancy doesn't just transform the body — it also triggers profound change to the brain and reflects another critical period of brain development.'
She called this remodeling an often-overlooked period of brain development that takes place well into a woman's adulthood.
How alarmed should women be?
Less gray matter may not sound very positive, but it happens for a reason.
'Despite what one might think, these reductions are not a bad thing, and in fact, are to be expected,' Pritschet said, noting that some of the losses are eventually regained. 'This change could indicate a 'fine-tuning' of brain circuits, not unlike what happens to all young adults as they transition through puberty and their brain becomes more specialized.'
These changes could also be a response to the high physiological demands of pregnancy itself, she said, 'showcasing just how adaptive the brain can be.'
These changes could affect future health and behavior
Mapping these changes could open the door to understanding an array of other neurological and behavioral outcomes including postpartum depression, headaches, migraines, epilepsy, stroke and parental behavior.
'The neuroanatomical changes that unfold during (pregnancy) have broad implications for understanding vulnerability to mental health disorders … and individual differences in parental behavior,' said Pritschet.
It may even provide critical insight into how the brain changes over a lifespan, she said.