How does the brain change during pregnancy?

• The female body goes through a variety of physical changes during pregnancy, including alterations to the brain.
• Most of the changes are due to pregnancy hormones.
• Researchers from the University of California – Santa Barbara for the first time show how hormonal shifts alter the brain throughout pregnancy, including changes to the amount of white and gray matter in the brain.

During pregnancy, the female body goes through a variety of physical changes, including additional blood in the body, faster heart rate, increased work on the kidneys, deeper breathing, and alterations to the digestive tract that may cause heartburn, nausea, or vomiting.

Previous research shows that pregnancy hormones can also cause changes in the brain.

Now, researchers from the University of California — Santa Barbara have for the first time shown how hormonal shifts alter the brain throughout pregnancy, including changes to the amount of white and gray matter in the brain.

For this study, researchers followed a 38-year-old woman, taking 26 magnetic resonance imaging (MRI) scans and blood draws starting 3 weeks preconception up to 2 years following childbirth.

“The brain is an endocrine organ, and sex hormones are potent neuromodulators, but a lot of that knowledge comes from animal studies,” Emily G. Jacobs, PhD, associate professor of Psychological & Brain Sciences at the University of California – Santa Barbara and senior author of this study explained to Medical News Today.

“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. 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,” she pointed out.

“My lab here at UC Santa Barbara uses precision imaging methods to understand how the brain responds to major neuroendocrine transitions — the circadian cycle, the menstrual cycle, menopause, and now one of the largest neuroendocrine transitions that a human can experience, pregnancy,” Jacobs told us.

Upon analyzing the MRI scans, Jacobs and her team discovered the most noticeable changes to the study participant’s brain throughout her pregnancy was a reduction in cortical gray matter volume, which persisted after giving birth.

The majority of the outside layer of the brain consists of gray matter, which has a main job of processing information in the brain and helps control thoughts, emotions, memory, and muscle movement.

“Sometimes people bristle when they hear that gray matter volume decreases during pregnancy, but this probably isn’t 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.”

“Think of Michealangelo’s David,” she illustrated. “The artist starts with a block of marble and the underlying beauty is revealed through the art of removal by carefully honing and fine-tuning the material. With the brain, this process happens early in development, again during puberty, and pregnancy probably reflects another wave of cortical refinement.”

Additionally, scientists found noteworthy increases in white matter located deeper in the brain, which they reported peaked in the second trimester and returned to normal pre-pregnancy levels around the time of birth.

About 60% of the brain consists of white matter, which connects different areas of the brain together to help with communication for focus, learning, and balancing while moving.

“There is so much about the neurobiology of pregnancy that we don’t understand yet,” Jacobs said. “It’s not because women are too complicated; it’s not because pregnancy is some Gordian knot. It’s a byproduct of the fact that the biomedical sciences often ignore women’s health. It’s 2024 and this is the first glimpse we have at this fascinating neurobiological transition and our ignorance has consequences.”

“Scientists don’t have the data we need to predict postpartum depression before it manifests; we don’t have the data we need to understand the effects of preeclampsia on later life brain health,” she continued.

“We need better data. Women are half of the population, but only [approximately] 10% of the NIH [National Institutes of Health] budget goes to conditions that primarily affect women. Of the 50,000 human brain imaging articles published in the last 30 years, less than half of 1% focus on health factors unique to women. So when we talk about the ‘scientific body of knowledge’ let’s consider, whose body does it serve?”

– Emily G. Jacobs, PhD

After reviewing this study, Clifford Segil, DO, neurologist at Providence Saint John’s Health Center in Santa Monica, CA, told MNT he found this research to be fascinating and thought-provoking.

“I think it is so cool that we [can] image a woman’s brain while pregnant with an MRI without causing any harm to the mother and their developing baby as MRI does not use radiation and wiggle people’s electrons,” Segil told us.

“It is fascinating to see data that suggests a pregnant mother has a transient increase of white matter with a decrease in gray matter while pregnant,” he added.

However, he also noted that the research highlights just how many questions about brain changes in pregnancy still remain unanswered. Chief among these is: What purpose do these changes actually serve?

“The way that I describe gray matter is a computer room full of servers and computers and the gray matter is all of the computers on these server racks,” said Segil.

And, he continued, “the way that I describe white matter is a computer room with countless wires, extension cords, networking cables and the white matter is all of these interconnections.“

“During pregnancy, this paper demonstrated, the mom [whose case the researchers] studied had a decrease in the amount of ‘computers’ running, with an increase in the amount of ‘cables’ running around her brain. Imagine a room with extra surge protectors, extension cords, network wires is like a pregnant woman’s brain, which is fascinating. Like many things in neuroscience, the next step will be to ask why and how this knowledge can help a pregnant woman’s health.”

– Clifford Segil, DO

MNT also spoke with G. Thomas Ruiz, MD, a board-certified OB/GYN and lead OB/GYN at MemorialCare Orange Coast Medical Center in Fountain Valley, CA, about this study.

Ruiz, who was also not involved in the study, said is it very important for researchers to continue to find ways in which pregnancy impacts different parts of the body, such as the brain.

“It’s really important because there are some really negative impacts that can occur with hormones of pregnancy, specifically depressive states and , which is a major mental health issue,” Ruiz explained.

“So you really want to understand those processes to come up with better, more viable treatments for these types of disorders, because you’re talking about mood disorders,“ he emphasized.

“I think [researchers] need to continue to take a look at the complete interaction of hormones with neurotransmitters, so that we can get an accurate true understanding of how this interaction occurs,” Ruiz concluded.