Pregnancy is a transformative time in a woman’s life, and during pregnancy her body undergoes rapid physiological adaptations to prepare for motherhood. We all know this, but what has remained a mystery is how the profound hormonal changes that occur affect the brain. Now, a team of researchers from Professor Emily Jacobs’ laboratory at the University of California, Santa Barbara, has revealed details on this topic.
The group has published a pioneering map of the human brain throughout pregnancy in the journal Nature Neuroscience. “We wanted to look at the trajectory of brain changes specifically during the gestational period,” explained Laura Pritschet, lead author of the study. Previous studies had captured images of the brain before and after pregnancy, but until now the brain had not been observed in full transformation during pregnancy.
The results, in addition to questioning the belief about the “fragility of women during pregnancy,” have implications that go beyond the study of the female brain, providing relevant information on human neuroplasticity in general. According to the data obtained, some areas of the brain reduce in size during pregnancy, although their connectivity improves, while few regions remain intact during the transition to motherhood.
Following a woman who was about to become a mother for the first time, researchers scanned her brain every few weeks, starting before pregnancy and continuing until two years after delivery. The data, obtained in collaboration with Elizabeth Chrastil’s team at UC Irvine, reveal changes in both gray and white matter throughout pregnancy, suggesting that the brain has a remarkable capacity for neuroplasticity even in adulthood.
The precision of the images allowed them to capture a dynamic reorganization of the brain in extraordinary detail. This approach complements previous studies that compared the brains of women before and after pregnancy. “Our goal was to fill the gap and understand the neurobiological changes that occur during pregnancy itself,” the authors comment.
Changes in the gray and white matter of the pregnant woman’s brain
The most notable changes the scientists found over time were a decrease in the volume of cortical gray matter, the wrinkled outer part of the brain. Gray matter volume decreased as hormone production increased during pregnancy. However, this reduction is not necessarily negative, according to the researchers. It could represent a “fine-tuning” of brain circuits, similar to what happens in young people during puberty, when the brain becomes more specialized. Pregnancy likely reflects another period of cortical refinement.
Although less obvious, another significant finding was the increase in white matter, located deeper in the brain and largely responsible for facilitating communication between different brain regions. While the reduction in gray matter persisted long after delivery, the increase in white matter was transient, peaking in the second trimester and returning to pre-pregnancy levels around the time of birth.
The changes suggest that the adult brain is capable of undergoing a prolonged period of neuroplasticity, which could facilitate behavioral adaptations related to parenting.
This type of effect had not been previously recorded with before-and-after scans, which allowed the researchers to better estimate how dynamic the brain can be in a relatively short period of time. “The maternal brain undergoes a choreographed change during gestation, and we can finally observe how it develops,” Jacobs said. These changes suggest that the adult brain is capable of undergoing a prolonged period of neuroplasticity, which could facilitate behavioral adaptations related to parenting.
“Around 85% of women experience pregnancy one or more times during their lifetime, and around 140 million women are pregnant every year,” explained Pritschet, who hopes to “debunk the myth” of women’s fragility during pregnancy. She argued that the neuroscience of pregnancy should not be considered a minor research topic, as findings from this field will deepen the general understanding of the human brain, including its aging process.
The open-access dataset is a starting point for future studies seeking to understand whether the magnitude or speed of these brain changes can offer clues about the risk of postpartum depression, a neurological condition that affects one in five women. “There are currently FDA-approved treatments for postpartum depression,” Pritschet said, “but early detection remains elusive. The more we learn about the maternal brain, the better chance we have of offering relief.”
That’s precisely what the authors set out to do. With support from the Ann S. Bowers Initiative for Women’s Brain Health, led by Jacobs, her team is expanding on these early findings through the Maternal Brain Project. More women and their partners are being enrolled at UC Santa Barbara, UC Irvine and in international collaboration with researchers in Spain.
“Experts in neuroscience, reproductive immunology, proteomics and artificial intelligence are coming together to learn more than ever about the maternal brain,” Jacobs said. “Together, we have the opportunity to address some of the most pressing and least understood issues in women’s health.”
