Pregnancy changes the brain’s white and gray matter
We all know that a woman’s body goes through countless physical changes during pregnancy, most of which are due to hormones. These range from increased heart rate and deeper breathing to an increased blood supply and changes to the digestive tract. (Remember heartburn, nausea, and vomiting, ladies?)
But a new study out of the University of California, Santa Barbara has shown how these hormonal shifts during pregnancy also change the amount of gray and white matter in the mother’s brain.
The research was published in the September 16, 2024, edition of the journal Nature Neuroscience.
The Research
A team of scientists led by senior author and UC Santa Barbara Psychological and Brain Sciences Associate Professor Dr. Emily Jacobs wanted to see how the brain changes day to day or week to week during pregnancy.
They followed a pregnant woman from 3 weeks preconception to 2 years after childbirth, drawing blood at various intervals and taking 26 MRI scans to view these changes in the brain as hormone levels changed. Why only one woman?
“Human studies tend to rely on brain imaging and endocrine assessments that are collected from groups of people observed at a single point in time,” explained Jacobs. “But that kind of group averaging approach can’t tell us anything about how the brain is changing day to day or week to week, as hormones ebb and flow.”
According to Jacobs, the UC Santa Barbara lab features equipment capable of using precise imaging methods to understand how the brain responds to major neuroendocrine transitions—from the circadian cycle and the menstrual cycle to menopause and pregnancy.
Decreases in gray matter
Among the most noticeable changes discovered through the use of MRI scans was the reduction in cortical gray matter. This lasted throughout the woman’s pregnancy and continued after she gave birth. This outer layer of the brain is charged with processing information and it helps control memory, emotions, thoughts, and muscle movement.
While it might sound scary to hear that gray matter volume decreases during pregnancy, Jacobs points out that it’s probably not a bad thing. “This change reflects the fine-tuning of neural circuits, not unlike the cortical thinning that happens during puberty. In both cases, this adaptive process enables the brain to become more specialized.”
Increases in white matter
Another observed change during pregnancy? A noteworthy increase in white matter. This deeper-set matter connects areas of the brain to assist with communication for learning, focus, and balancing while moving.
White matter typically makes up about 60% of the brain, although pregnancy appears to increase white matter, peaking during the second trimester and returning to normal pre-pregnancy levels around the time the woman gives birth.
How the results may help women’s health
So, how might these findings help improve women’s health in the future? One immediate condition that comes to mind is postpartum depression, something that’s largely tied to post-pregnancy hormones.
Understanding how and when the brain changes during and after pregnancy in relation to hormones can give scientists and doctors a better understanding of how best to treat mood disorders like depression.
MBJ
Wendy Burt-Thomas writes about the brain, mental health and parenting.
Check out the original research:
