Scans capture dramatic brain reorganization during pregnancy

For the first time, profound changes in the human brain during pregnancy have been documented after researchers performed precise scans of a woman carrying her child.

MRI scans taken every few weeks from before conception until two years after delivery showed widespread reorganization in the mothers’ brains. Some changes were short-lived, others lasted for years.

The work, described by an independent expert as “truly heroic”, paves the way for a much deeper understanding of the mother’s brain during pregnancy. More scans are now being collected from other pregnant women to learn more about the risks of postnatal depressionthe connection between preeclampsia and dementiaand why pregnancy can reduce migraines And symptoms of multiple sclerosis.

Scientists took 26 brain scans of a healthy 38-year-old woman who became pregnant through IVF, as well as concurrent blood samples to monitor the dramatic hormone surges during pregnancy. The data revealed how the brain changed week after week.

Most striking was a steady decrease in gray matter, the wrinkled outer surface of the brain, throughout pregnancy and a temporary spike in neural connectivity at the end of the second trimester.

“The mother’s brain undergoes this choreographed change during pregnancy and we can finally observe the process in real time,” said Prof. Emily Jacobs, a researcher on the study from the University of California, Santa Barbara.

Scientists have previously taken snapshots of women’s brains during different stages of pregnancy. However, the latest research shows that this can miss temporary changes that return to normal by the time the woman gives birth.

Write in Nature Neurosciencelead author Laura Pritschet and her colleagues describe how rising hormones such as estrogen and progesterone trigger significant physiological changes during pregnancy, affecting blood plasma, metabolism, oxygen consumption, and immunity. The same hormones reshape the brain.

To understand more, the researchers used precision MRI to scan the brain of Dr. Elizabeth Chrastil, a fellow at the University of California, Irvine. She was scanned before conception, during pregnancy, and for two years after her son was born in May 2020.

“It was a pretty intense undertaking,” Chrastil said, but added that she didn’t really feel any different during the pregnancy. “Some people talk about ‘mummy brain’ and things like that, and I didn’t really experience any of that.”

The scans showed widespread reductions in gray matter volume and thickness, particularly in areas involved in social cognition. White matter microstructure, a measure of the brain’s wiring, increased to a peak at the end of the second trimester before declining again. The cerebrospinal fluid and the brain’s cavities, known as ventricles, both expanded. The changes were linked to rising hormone levels.

“Sometimes people get upset when they hear that gray matter volume decreases during pregnancy,” Jacobs said. “This change likely reflects fine-tuning of neural circuits, similar to the cortical thinning that occurs during puberty.” The researchers compared the process to sculpting Michelangelo’s David from a block of marble.

The study doesn’t explain the behavior or emotions that emerge during pregnancy, and there are many factors at play beyond hormones, such as stress and lack of sleep. But some of the brain changes persisted two years after delivery, suggesting cellular changes in the organ. “This paper really raises more questions than it answers,” Chrastil said. “We’re just scratching the surface.”

The work marks the launch of the Mother Brain Projectan international effort to collect similar scans from more pregnant women. Jacobs said: “There’s so much about the neurobiology of pregnancy that we don’t understand yet and that’s not because women are too complicated, it’s not because pregnancy is some kind of Gordian knot, it’s a byproduct of the fact that the biomedical sciences have historically ignored women’s health.”

Gina Rippon, emeritus professor of cognitive neuroimaging at Aston University in Birmingham, England, said it was a “truly heroic” project, adding: “The data from this study illustrates how much we have been missing.”

Dr. Ann-Marie de Lange, the leader of the FemiLab group at the University Hospital of Lausannecalled the work “fascinating.” “This approach will not only help us map maternal neuroplasticity, but also identify markers of risk for postpartum depression, a serious condition that often goes untreated,” she said.