This is your brain on pregnancy

by Sonia Fernandez

Pregnancy is a transformative time in a person’s life, when the body undergoes rapid physiological adaptations to prepare for motherhood. That much we all know. What has remained something of a mystery is what the sweeping hormonal shifts brought on by pregnancy are doing to the brain. Not anymore. Researchers in Professor Emily Jacobs’ lab have shed light on this understudied area with the first-ever map of a human brain over the course of pregnancy. “We wanted to look at the trajectory of brain changes specifically within the gestational window,” says Laura Pritschet, a graduate student with Jacobs and lead author of a paper published in the journal Nature Neuroscience. Previous studies had taken snapshots of the brain before and after pregnancy, but never has the pregnant brain been witnessed in the midst of this metamorphosis

Following one first-time mother, the researchers scanned her brain every few weeks, starting before pregnancy and continuing through two years postpartum. The data, collected in collaboration with professor Elizabeth Chrastil’s team at UC Irvine, reveal changes in the brain’s gray and white matter across gestation, suggesting that the brain is capable of astonishing neuroplasticity well into adulthood. Their precision imaging approach allowed them to capture dynamic brain reorganization in the participant in exquisite detail, complementing early studies that compared women’s brains pre- and post-pregnancy. “Our goal was to fill the gap and understand the neurobiological changes that happen during pregnancy itself,” they noted.

Decrease in gray matter, increase in white matter

The most pronounced changes the scientists found as they imaged the subject’s brain over time was a decrease in cortical gray matter volume, the wrinkly outer part of the brain. Gray matter volume decreased as hormone production ramped up during pregnancy. A decrease in gray matter volume is not necessarily a bad thing, the scientists emphasized. 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 brains become more specialized. Pregnancy likely reflects another period of cortical refinement.

Less obvious but just as significant, the researchers found prominent increases in white matter, located deeper in the brain and generally responsible for facilitating communication between brain regions. While the decrease in gray matter persisted long after childbirth, the increase in white matter was transient, peaking in the second trimester and returning to pre-pregnancy levels around the time of birth. This type of effect had never been captured previously with before-and-after scans, according to the researchers, allowing for better estimation of just how dynamic the brain can be in a relatively short period of time.

“The maternal brain undergoes a choreographed change across gestation, and we are finally able to see it unfold,” Jacobs says.

“Eighty-five percent of women experience pregnancy one or more times over their lifetime, and around 140 million women are pregnant every year,” says Pritschet, who hopes to “dispel the dogma” around the fragility of women during pregnancy. The neuroscience of pregnancy should not be viewed as a niche research topic, she argues, as the findings generated through this line of work will “deepen our overall understanding of the human brain, including its aging process.”

And that is just what they have set out to do. With support from the Ann S. Bowers Women’s Brain Health Initiative, directed by Jacobs, the team is building on these early discoveries through the Maternal Brain Project. More women and their partners are being enrolled at UC Santa Barbara, at UC Irvine, and through an international collaboration with researchers in Spain.

“Experts in neuroscience, reproductive immunology, proteomics and AI are joining forces to learn more than ever about the maternal brain,” Jacobs says. “Together, we have an opportunity to tackle some of the most pressing and least understood problems in women’s health.”