Pregnancy changes women’s brains profoundly

In my late twenties, while studying how the brain changes through therapy and meditation, a simple question from a colleague surprised me: how does pregnancy reshape the human brain?

I was working as a postdoctoral researcher in Barcelona, running a series of longitudinal brain imaging studies. With one of my PhD students, Elseline Hoekzema, we were exploring how cognitive therapy reshaped the brains of children with attention-deficit/hyperactivity disorder. With another, Erika Barba-Müller, we were looking into how daily meditation could transform the human brain. None of us had children, but one day Erika told us she was planning to become pregnant. We congratulated her, and after a conversation that shifted between personal and work topics, Erika said: “What if we study the mother’s brain?” We realised that none of us knew anything about it.

We looked on PubMed. All we could find were plenty of papers on animals, mainly rodents, and practically nothing on humans. So, the three of us started designing a study to answer this question. When Erika became pregnant, she joined as one of the experimental participants. Elseline and I were among the control participants. This project was the subject of Erika’s thesis, which I supervised.^[1]

We evaluated the women’s brains before they conceived and after birth. We also included a group of women who had never given birth or experienced pregnancy. The results astounded us.

We found that the changes in a woman’s brain during the matrescence period are very profound – more than I have ever seen before. For comparison, if you train machine learning algorithms to look at a structural brain image and say if this person has schizophrenia or not, they can be accurate approximately 60% of the time. But when looking at two brain images of a woman, we can tell with 100% accuracy whether or not she has gone through pregnancy between those images being taken.

It shouldn’t be surprising that pregnancy changes a woman’s brain so profoundly. Nearly all the systems of the human body need to adapt during pregnancy, including the immune system and the cardiovascular system, so why not the brain? But it was very surprising that nobody had investigated this question, especially when the results were so solid and robust, and their implications for perinatal care groundbreaking.

Brain changes are an essential part of becoming a mother

Longitudinal research tracking the effects of pregnancy and motherhood are especially challenging. We started the project in 2008, and the research was finally published in 2017.^[2] During that period, I became a mother myself.

By this point in the research, I already knew that pregnancy would fundamentally change my own brain. In some ways, that was a scary thought – but it was also reassuring to know that it happens to everyone. It’s like adolescence: it’s frightening to feel yourself changing, but it helps to know that this is a normal transition – a necessary period of growth and transformation that will help you find yourself and create meaning.

We found that in pregnancy there is a steep decline in grey matter in the woman’s brain. People hear this as a bad thing, but it isn’t – it happens in adolescence too. There’s a common misperception that becoming a mother makes you function less well cognitively – the idea of “baby brain” – but that’s not what we found at all. There was no association between brain changes and cognitive scores.

Instead, we found that these brain changes were associated with scores on maternal–infant bonding – the bigger the change, the stronger the bonding. In a poetic way, I like to explain it as clearing a field of what had been growing before, so you can plant new seeds and something different grows. The grey matter partially recovers again after giving birth, but it builds back at different rates.

Certain parts of the brain seem not to go back to baseline levels, including regions that are involved in internal processing, self-perception and empathy. This aligns with psychological and popular knowledge; when a baby is born, a mother is born, and it seems you don’t perceive yourself in the same way that you did before. It also matches my personal experience. My first feeling on looking at my daughter was that of a division, as if my self had been divided when I gave birth.

When my daughter laughed, I felt her joy in my guts. When she was ill, I resonated with her pain in my own body. The synchrony, the fusion, is amazing. You have this sense that you’re no longer the only protagonist in the movie of your life.

A research opportunity that will be a breakthrough for perinatal care

We soon realised that the profound changes we detected in our first study were just the tip of the iceberg. A lot of other questions came to our minds. For example, what is the role of hormones in these changes? How do changes in the brain relate to changes in the cardiovascular system or the immune system? What happens in subsequent pregnancies? What about fathers and other significant caregivers? We are only starting to understand pieces of a much larger puzzle.

We also see potential to transform how we support mothers’ mental health after birth. Currently, postpartum depression is diagnosed using clinical interviews. But if we can map what neurotypical changes to the brain look like during pregnancy, and compare them with the changes in mothers with postpartum depression, we could improve our ability to predict and prevent depression.

We are already making progress towards answering some of these questions. For example, we are currently analysing data from the BeMother Project^[3], which I co-lead with Óscar Vilarroya, who was my PhD supervisor. The data have revealed how these changes are modulated by oestrogen levels, and how brain changes predict mother–infant bonding, an association that is mediated by maternal wellbeing.

With Nina Miolane, an AI expert at the University of California Santa Barbara (UCSB), we are creating the first “digital twin” of the maternal brain.^[4] This is a virtual replica of a real brain – trained on real data – that will allow us to simulate, monitor, and predict brain changes given certain variables. It can serve as an educational tool and will eventually be integrated into pregnancy apps to illustrate how a woman’s body, including the brain, adapts during this period.

And together with two international initiatives, the Ann S. Bowers Women’s Brain Health Initiative and Enigma Neuroendocrinology^[5][6], we are contacting researchers in different parts of the globe – from New Zealand to United States – to compare how changes in the maternal brain may be modulated by differences in social and cultural contexts. This is a very exciting and thrilling collaboration with Emily Jacobs and Magdalena Martínez at UCSB.

We are now seeking to enrol thousands of participants for these global studies. It’s a significant commitment, as we collect a lot of data – surveys, neuropsychological evaluations, clinical data biomarkers, fluid biomarkers, hormones – from preconception through pregnancy and postpartum. It is also expensive, so we need sustained support from funders to make it possible.

So far, we have found that women are enthused about getting involved. Once they realise how little is known about the phenomenon of brain changes in motherhood, they are motivated by a sense of sorority to contribute to expand that knowledge. Often, when they give birth, they send us a photo from the hospital with their baby. It’s amazing to feel part of this moment in their lives. Each image, each scan and each story helps us understand how motherhood transforms us.