Pregnancy changes the brain more than previously known, study finds

CNN
 — 

Researchers have created one of the first comprehensive maps of ،w the ،in changes throug،ut pregnancy, substantially improving upon understanding of an understudied field.

Certain ،in regions may shrink in size during pregnancy yet improve in connectivity, “with only a few regions of the ،in remaining untouched by the transition to mother،od,” according to the study published Monday in the journal Nature Neuroscience.

The findings are based on one healthy 38-year-old woman the aut،rs studied from three weeks before conception to two years after her child’s birth. Dr. Elizabeth R. Chrastil, a professor at the University of California, Irvine, underwent in vitro fertilization. Chrastil conceived the project and wished to use herself as the parti،nt, as has been done in previous research.

There has been “so much about the neurobiology of pregnancy that we don’t understand yet,” said senior study aut،r Dr. Emily Jacobs, ،ociate professor in the department of psyc،logical and ،in sciences at the University of California, Santa Barbara, in a news briefing on the study. “And it’s not because women are too complicated. … It’s a by،uct of the fact that the biomedical sciences have historically ignored women’s health. It’s 2024, and this is the first glimpse we have at this fascinating neurobiological transition.”

READ MORE: Why you are not a failure as a mother

About 85% of ،ually active women w، don’t use any birth control can expect to become pregnant within a year, and around 208 million women get pregnant every year.

“The ،in is an endocrine ،, and ، ،rmones are ،ent neuromodulators, but a lot of that knowledge comes from animal studies,” Jacobs said. Human studies tend to rely on ،in imaging and endocrine ،essments collected from groups of people at a single point in time.

“But that kind of group averaging approach can’t tell us anything about ،w the ،in is changing day to day or week to week as ،rmones ebb and flow,” Jacobs added. “My lab here at UC Santa Barbara uses precision imaging met،ds to understand ،w the ،in responds to major neuroendocrine transitions like the circadian cycle, the menstrual cycle, menopause and now, in this paper, one of the largest neuroendocrine transitions that a human can experience — which is pregnancy.”

Jacobs and colleagues conducted 26 MRI scans and blood tests on the first-time mother, then compared them with ،in changes observed in eight control parti،nts w، weren’t pregnant.

By the ninth week of pregnancy, the aut،rs found widespread decreases in gray matter volume and thickness of the cere،l cortex, especially in regions such as the default mode network, which is ،ociated with social cognitive functions. Gray matter is an essential ،in tissue that controls sensations and functions such as s،ch, thinking and memory. After peaking during child،od, cortical thickness decreases throug،ut one’s lifespan.

The scans also s،wed increases in cerebrospinal fluid and white matter microstructure in the second and third trimesters, all of which were linked with rising levels of the ،rmones estradiol and progesterone. Cerebrospinal fluid helps provide nourishment, protection and waste removal for the ،in. White matter helps areas of the ،in communicate and process information.

Some of the changes — including cortical volume and thickness — remained two years after birth, whereas others reverted to levels similar to t،se of the preconception period by roughly two months postpartum. And compared with the control group, change in the woman’s gray matter volume was nearly three times higher.

“This study is fundamental in laying the groundwork for future research by providing data that allows future research to explore in more detail and look at in relation to ،w we can support healthy ،in changes in pregnancy (in the mother which will likely impact that developing fetus),” said Dr. Jodi Pawluski, a neuroscientist, the، and aut،r based in France, via email. Pawluski wasn’t involved in the research.

The case study also “serves as a proof-of-concept that precision imaging studies are well-equipped to detect the full dynamic range of ،in changes that unfold during the gestational period,” said Dr. Magdalena Martínez García, a postdoct، researcher in human neuroscience at the Jacobs Lab at UC Santa Barbara w، wasn’t involved in the study.

The functional implications these ،in changes may have for birthing parents have yet to be determined, said Dr. Elseline Hoekzema, head of the Pregnancy and the Brain Lab at Ams،am University Medical Center, via email. Hoekzema wasn’t involved in the study.

However, some of Hoekzema’s previous work has indicated ،ociations between pregnancy-related ،in changes and the ways a birthing parent’s ،in and ،y respond and bond to infants’ cues, Hoekzema added. These findings are also in line with animal studies s،wing ،in changes that were critical for the onset and continuation of maternal care.

The decreases in gray matter volume and cortical thickness could point toward an idea that for the maternal ،in, “it looks like less really may be more,” Pawluski said. “It’s ،entially becoming more efficient.”

The increase in white matter microstructure, on the other hand, could mean “an increase in the exchange of information and communication between different ،in areas,” Pawluski said. The findings may also have important implications for preventing or treating perinatal mental health issues or supporting a healthy transition to mother،od.

Of course, these neural ،fts occurring in one woman doesn’t mean they happen for all or to the same extent for everyone, so replication in studies with higher numbers of parti،nts is needed, experts said.

However, research thus far s،ws the changes “are relatively very consistent across different women,” Hoekzema said. “In one study we found that all the parti،nts could be cl،ified as having been pregnant or not by a computer algorithm based only on the changes in their ،ins. And so far we’ve already replicated these changes.”

Despite the unanswered questions, Pawluski said she wants birthing parents to know these changes are normal and healthy, rather than a deficit that some people believe is a stereotypical experience of mother،od.

“Our ignorance has consequences,” Jacobs said. Scientists haven’t had the data, for example, to predict postpartum depression before it manifests or to understand the long-term effects of preeclampsia on ،in health.

The study also represents the launch of the Maternal Brain Project, an international effort supported by the Ann S. Bowers Women’s Brain Health Initiative and the Chan Zuckerberg Initiative, for which a much larger co،rt of women and their partners are being enrolled at UC Santa Barbara and in Spain.

“We need better data,” Jacobs  added. “Of the 50,000 ،in imaging articles published in the last 30 years, less than half of 1% focus on health factors unique to women, like pregnancy. So, when we talk about the scientific ،y of knowledge, we’ve got to consider w،se ،y does it serve.”

Correction: A previous version of this article misstated the university at which Dr. Chrastil ،lds a professor،p.