Pregnancy can actually shrink parts of a woman's brain, study finds!

For decades, pregnant women’s forgetfulness and ditzyness have been labelled ‘pregnancy brain’. The momiker is casually thrown around to describe what is a life-altering experience and a new mother’s lack of sharpness has always been attributed to lack of sleep and exhaustion. However, new research has shown that pregnancy does actually, physically, alter the brain!

The fascinating study has revealed that pregnancy can shrink grey matter in more than 80% of a woman’s brain, leaving lasting "permanent etchings" in the brain.

Led by Emily Jacobs, an associate professor at the University of California, Santa Barbara (UCSB), the study examined the brain of Liz Chrastil, a neuroscientist from UC Irvine, who volunteered for over two dozen MRI scans throughout her pregnancy and two years postpartum. These scans provided a rare and detailed insight into the neurological changes women undergo during and after pregnancy.

A 4% decrease in grey matter

Grey matter, the part of the brain responsible for processing information and containing the connections between neurons, showed a significant reduction during pregnancy. On average, there was a 4% decrease in volume in the affected brain areas. According to Jacobs, this reduction mirrors the changes that occur during puberty when hormonal surges prompt the brain to prune excess tissue and optimise neural circuits. Pregnancy may trigger a similar "fine-tuning" process.

“Sometimes people bristle when they hear that grey-matter volume decreases during pregnancy — like, ‘That can't be a good thing,’” Jacobs noted during a press conference. “However, this change probably reflects the fine-tuning of neural circuits, not unlike the cortical thinning that happens during puberty.”

This fine-tuning could leave long-lasting changes in the brain. Jacobs referred to these modifications as "permanent etchings," suggesting that the neurological impacts of pregnancy may be long-lasting.

The role of white matter

While grey matter shrank, white matter, the brain’s insulated wiring that helps transmit information between neurons, initially grew stronger during pregnancy. In the early stages of pregnancy, Chrastil’s brain showed a marked increase in the "microstructural integrity" of white matter, which supports more efficient neural communication.

"We think of it as like a tube or a straw," Chrastil explained, emphasising that when white matter is strong, it helps information flow more efficiently, much like water moving cleanly through a tube. However, by the time of birth, the white matter had returned to its baseline state.

Implications for maternal health

The significance of these findings extends beyond curiosity about how the brain adapts to motherhood. The study could have major implications for understanding pregnancy complications and neurological conditions. For example, conditions like preeclampsia, which affects blood vessels and increases the risk of stroke and vascular dementia, may be linked to brain changes. Similarly, understanding why conditions like migraines and multiple sclerosis often improve during pregnancy could lead to new medical insights.

Although this study focused on just one individual, the researchers noted that their findings are consistent with larger studies of first-time mothers. Magdalena Martínez-García, a postdoctoral researcher in human neuroscience at UCSB, mentioned that these changes may be a "ubiquitous phenomenon" for new mothers.

To explore this further, the researchers have launched the Maternal Brain Project, an international initiative aimed at collecting brain scans from more pregnant individuals. According to Jacobs, preliminary results are already showing similar patterns of change in other participants, reinforcing the idea that pregnancy could universally shape the maternal brain.

A new frontier in understanding motherhood

The changes discovered in this study challenge traditional views of pregnancy and the brain. Instead of simply being a "mommy brain" fog often joked about, these changes may represent a powerful form of neurological adaptation.

As researchers continue to map the maternal brain, there is hope that these insights will pave the way for better healthcare outcomes for mothers. From identifying early signs of pregnancy-related complications to understanding long-term changes, studies like this one may soon shift how we approach maternal health and well-being.

In the end, these findings highlight the remarkable resilience and adaptability of the human brain, as well as the profound and lasting impact of motherhood on the mind.