New study reveals brain changes throughout pregnancy

Pregnancy is a transformative time in a person’s life, during which the body undergoes rapid physiological adaptations to prepare for motherhood. We all know this. What remains a mystery is how the radical hormonal changes caused by pregnancy affect the brain. Researchers in Professor Emily Jacobs’ lab at the University of California, Santa Barbara, have shed light on this little-studied area by conducting the first mapping of the human brain during pregnancy.

“We wanted to look at the trajectory of brain changes specifically during the gestational window,” said Laura Pritschet, lead author of a paper published in Neuroscience of NaturePrevious studies have taken snapshots of the brain before and after pregnancy, she said, but we’ve never seen a pregnant woman’s brain in the midst of this metamorphosis.

The researchers followed a first-time mother and scanned her brain every few weeks, starting before pregnancy and continuing for two years after giving birth. The data, collected in collaboration with Elizabeth Chrastil’s team at UC Irvine, reveal changes in the brain’s gray and white matter throughout gestation, suggesting that the brain is capable of astonishing neuroplasticity well into adulthood.

Their precision imaging approach allowed them to capture the dynamic reorganization of the participants’ brains in exquisite detail. This approach complements earlier studies that compared women’s brains before and after pregnancy. The authors noted, “Our goal was to fill this gap and understand the neurobiological changes that occur during pregnancy itself.”

Decreased gray matter, increased white matter

The scientists observed a decrease in the volume of cortical gray matter, the wrinkled outer part of the brain, which shrank as hormone production increased during pregnancy. However, a decrease in gray matter volume is not necessarily a bad thing, the scientists stressed.

This change could indicate a “fine-tuning” of brain circuits, much like what happens in all young adults as they transition into puberty and their brains become more specialized. Pregnancy likely reflects another period of cortical refinement.

“Laura Pritschet and the study team have achieved a tour de force, conducting a rigorous series of analyses that have generated new insights into the human brain and its incredible capacity for plasticity in adulthood,” Jacobs said.

Less obvious but equally significant, the researchers found a significant increase in white matter, which is located deeper in the brain and is typically responsible for facilitating communication between brain regions. While the decrease 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 by the time of birth.

This type of effect has never been captured before with before-and-after scans, the researchers said, allowing for a better estimate of how dynamic the brain can be in a relatively short period of time.

“The maternal brain undergoes programmed changes throughout gestation, and we’re finally able to observe them,” Jacobs said. These changes suggest that the adult brain is capable of undergoing a prolonged period of neuroplasticity, brain changes that may support behavioral adaptations related to parenting.

“85 percent of women experience pregnancy at least once in their lifetime, and about 140 million women are pregnant each year,” said Pritschet, who hopes to “dispel the dogma” around women’s fragility during pregnancy.

She argued that the neuroscience of pregnancy should not be considered a niche research topic, as the discoveries generated by this field of work “will deepen our overall understanding of the human brain, including its aging process.”

The open-access dataset, available online, serves as a starting point for future studies aimed at understanding whether the magnitude or pace of these brain changes holds clues to a woman’s risk for postpartum depression, a neurological condition that affects about one in five women.

“There are now FDA-approved treatments for postpartum depression,” Pritschet said, “but early detection remains difficult. The more we learn about the maternal brain, the better our chances of providing relief.”

And that’s exactly what the authors set out to do. Led by Jacobs, their team is building on these early findings through the Maternal Brain Project. More women and their partners are being recruited at UC Santa Barbara, UC Irvine, and through an international collaboration with researchers in Spain.

“Experts in neuroscience, reproductive immunology, proteomics and artificial intelligence are joining forces to learn more about the maternal brain than ever before,” Jacobs said. “Together, we have the opportunity to tackle some of the most pressing and poorly understood issues in women’s health.”