Study shows just how much pregnancy affects the brain—and it’s more than previously thought

We’ve all heard of “pregnancy brain.” But for the first time, researchers have actually created a comprehensive map of how the brain changes during pregnancy—and their study showed how little we previously understood about this area of science. Basically, pregnancy affects the brain A LOT.

The new study, published earlier this week in the journal Nature Neuroscience, revealed that some areas in the brain shrink in size but become better connected with one another, “with only a few regions of the brain remaining untouched by the transition to motherhood,” study authors wrote.

Dr. Elizabeth R. Chrastil, a professor at the University of California, Irvine, underwent in vitro fertilization, conceived the study, and used her own brain in the study. She’s a healthy 38-year-old. The study’s authors extensively studied her brain from  three weeks before conception to two years after her child’s birth.

There has been “so much about the neurobiology of pregnancy that we don’t understand yet,” study author Dr. Emily Jacobs, associate professor in the department of psychological and brain sciences at the University of California, Santa Barbara, said in a news briefing.

She added, “And it’s not because women are too complicated. It’s a byproduct 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.”

Most knowledge in this area comes from either animal studies or human studies that rely on brain imaging from a single point in time, Jacobs said. 

“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 continued. “My lab here at UC Santa Barbara uses precision imaging methods to understand how the brain 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.”

During this study, Jacobs and her team collected 26 MRI scans and blood tests and compared them to eight control participants who weren’t pregnant. By the ninth week of pregnancy, the researchers observed widespread decreases in gray matter volume and thickness of the cerebral cortex, especially in parts of the brain associated with social cognitive functions. Gray matter controls functions like speech, thinking, and memory. Typically, it peaks during childhood and decreases throughout the rest of our lives.

Scientists still don’t know why those changes happen, what their implications could be, or if they happen for everyone. Further study is needed with larger numbers of participants to better understand changes in the brain during pregnancy, they said. 

“We need better data,” Jacobs said. “Of the 50,000 brain 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 body of knowledge, we’ve got to consider whose body does it serve.”