Pregnancy changes the brain – and we are only beginning to understand how and why

Millions of women go through pregnancy every year, yet science has only just begun to look at what it does to the brain – the organ undergoing perhaps the most remarkable transformation. Over the past decade, a small group of scientists in Spain and the Netherlands has been mapping those changes in unprecedented detail.

The researchers scanned the brains of 127 first-time mothers five times: once before conception, twice during pregnancy, and again at one and six months after giving birth. It is the largest study of its kind ever conducted.

Brain imaging studies that follow the same people across pregnancy – with scans before conception and after birth – are extraordinarily difficult to run. Researchers must identify women planning to conceive, begin scanning before pregnancy begins, and then track them across months of physiological upheaval.

When a landmark 2017 study published in Nature Neuroscience first showed that pregnancy changes the brain’s structure, it included 25 first-time mothers. The new study has more than five times that number. This is a substantial leap.

What these 127 women’s brains showed was consistent and striking. Grey matter – the part of the brain densely packed with nerve cells – decreased by nearly 5% in several regions involved in emotion, empathy and social perception during pregnancy, reaching its lowest point in the final weeks before birth.

“I like to use the metaphor of pruning a tree,” Professor Susana Carmona, co-lead author of the study, recently told the BBC. “Some of the branches are cut to make it grow more efficiently.”

After delivery, it began to regain volume, around 3.4% by six months after giving birth. This pattern of change appeared across almost the entire surface of the brain, and it was seen in all women in the study without exception.

Crucially, this pattern did not appear in women who became parents during the study period without going through pregnancy themselves – for example, same-sex partners who were co-parenting a newborn but had not carried the baby. This suggests the observed brain changes are driven by the biology of pregnancy itself, rather than simply by the anticipation of becoming a parent.

The researchers also measured hormone levels and found that two forms of oestrogen tracked the brain changes closely, rising as grey matter volume fell and then declining sharply after birth when the placenta is delivered.

This connection between hormones and brain structure bridges decades of research in mice, where increased hormone levels during pregnancy have long been known to rewire the maternal brain and switch on caring behaviour.

Does the grey matter volume ever fully return?

In their most recently published study, the researchers found that at six months, some grey matter recovery continued. An earlier study from the same research group that followed mothers for six years after giving birth found that the brain changes were still detectable and still predicted how warmly mothers related to their children.

That study was able to correctly identify which women had been pregnant, based on brain scans alone, with more than 90% accuracy, even six years after birth. Far from being a temporary disruption, pregnancy appears to leave a lasting mark.

A Dutch study published in 2026 extended these findings, examining women during a second pregnancy. The brain changes recurred, but with a different pattern.

The regions most dramatically reshaped in a first pregnancy, those involved in self-awareness and reading others’ emotions, showed rather modest changes the second time around, as though the initial transformation had already been made. Instead, areas involved in attention and responsiveness to the outside world were more strongly affected, perhaps reflecting the additional demands of caring for a first child while pregnant.

The most consistent theme across all this research is that the regions most transformed are those involved in understanding other people: tracking intentions, feeling empathy and recognising signals. An imaging study published in Nature Neuroscience in 2024 scanned a single woman 26 times from before conception to two years after giving birth, providing an unprecedented map of the changes unfolding inside one brain across pregnancy – a resource now freely available to other researchers.

Comparison with teenage brains

A comparison with adolescent brains threads through all of this work. When the researchers directly compared the brain changes of pregnancy with those of adolescence – another life stage defined by surging sex hormones and profound behavioural shift – the patterns of change were almost identical. The same thinning of the cortex, the same flattening of the grooves on the brain surface, the same rate of brain volume change each month.

If adolescence reshapes the brain to prepare it for adult social life, the evidence now suggests that pregnancy reshapes it again – more specifically, more deeply – to prepare it for something even more demanding: caring for an infant.

What remains to be understood is what these changes mean at the level of cells and circuits, how they relate to almost one in five women who experience depression around the time of birth, and whether deviations from the typical pattern leave women more vulnerable or more resilient. The tools to begin answering those questions now exist. For the first time, there is a map.

Birgit Derntl receives funding from the German Research Foundation (DFG, International Research Training Group IRTG 2804), Hans und Ria Messer Stiftung as well as EU (MSCA doctoral network MenoBrain).

Ann-Christin S. Kimmig receives funding from the German Research Foundation (DFG, International Research Training Group IRTG 2804) and the German Academic Exchange Service (DAAD).

Franziska Weinmar receives funding from the German Research Foundation (DFG) as part of the International Research Training Group “Women’s Mental Health Across the Reproductive Years” (DFG, IRTG2804) and from the Hans und Ria Messer Stiftung.