Susana Carmona on the neurobiology of pregnancy

Susana Carmona wasn’t planning to start a new project in 2008. She was wrapping up her postdoctoral fellowship when an offhand conversation with two Ph.D. students snowballed into a long-term imaging study of pregnant women’s brains.

That study, along with subsequent work from Carmona, has proved foundational in describing the neurobiological fluctuations that women experience before, during and after pregnancy, and throughout motherhood.

Carmona seamlessly intertwines her life’s work in the lab with her own experiences in her new book, “A Mother’s Brain: The New Science of the Neuro-Maternal Revolution,” published today for the first time in English. In the following excerpt, she recounts the 2008 conversation that led to her study of pregnant women’s brains.

And in an interview with The Transmitter’s associate editor Francisco J. Rivera Rosario, Carmona shares why she wrote the book, reflects on when she fell in love with this line of research and discusses some of the major questions the field still needs to address.

In the fall of 2008, while Coldplay’s “Viva la Vida” was topping the charts, the world was sinking into the worst economic crisis I could remember. I was 28. I had a job in a research group run by Òscar Vilarroya. We worked in the Parc de Recerca Biomèdica de Barcelona, a gorgeous facility overlooking the sea. It had been less than a year since I’d defended my dissertation, and I knew that to have a scientific career in Spain, I needed to do an obligatory tour abroad. I was going to the United States—it had already been decided—but before taking the leap, I wanted to hang around Òscar’s lab for a couple more years. My excuse was that I had some projects to wrap up. I wasn’t planning to start anything new.

Vilarroya had a number of doctoral candidates in his lab, all women, all terrific researchers. I worked very closely with two of them, Elseline Hoekzema and Erika Barba-Müller, both because I was supervising their theses and because we were close friends outside the lab. Elseline’s thesis concentrated on cognitive therapy’s impact on the brains of children diagnosed with attention-deficit/hyperactivity disorder. Erika’s analyzed the consequences daily meditation practices have for the human brain. Both projects used longitudinal design, a methodology that involves observing the same subjects at more than one moment in time—in these cases, before and after a given intervention. The results Elseline found were promising, and we were already moving toward publication. Erika’s, not so much. Some of her subjects did show cerebral changes, but not all, and when we averaged out the results, the effect disappeared. I must add that although our study didn’t demonstrate pronounced changes brought on by a meditation practice, other, later studies have shown its beneficial impacts on the brain. 

This was the situation in our lab on November 5, 2008, when a casual conversation in the car changed the course of our careers. Erika was defending her master’s thesis that day. Her presentation couldn’t have been better, but we still came out of it with a bad taste in our mouths since the examiners, like us, knew the results weren’t consistent enough to publish. Still, Erika had defended successfully, and we weren’t going to not celebrate. The three of us got in my car and headed into Barcelona.

On the way, we started talking about the possible reasons we hadn’t observed a more pronounced effect on our meditators’ brains. We’d asked them to meditate for 30 minutes a day, but they admitted they didn’t always do it: Sometimes they forgot, and they more often fell asleep. We joked that my voice—I’d made the recordings they meditated to—was too soothing. At some point, Erika mentioned that she was trying to get pregnant. After our initial shock and congratulations, we continued to mix personal and professional topics, including how to give her thesis a new angle. We stopped at the lab, where the conversation we had started continued.

“What if we studied the brains of mothers?” Erika suggested.

“Getting pregnant and having a baby—that’s the perfect longitudinal study! No way your participants would flake. But you’d have to get into motherhood,” one of us said.

“Yeah, there wouldn’t be any ‘I didn’t feel like it’ or ‘I fell asleep,’” someone else agreed, laughing.

From there, we began talking about what we thought we knew about pregnancy’s impact on the mother’s brain. “I read that pregnant women score worse on memory and attention tests,” someone said.

“Wait, but I just read the opposite,” one of us shot back. “Mother rats do better on spatial-memory challenges, and the improvements last after weaning. I’m pretty sure their brains change permanently.”

We sat at a computer to do a quick search of PubMed, the main biomedical research online database. We started putting in terms that we thought would clarify what happens in a woman’s brain when she gets pregnant, but to our surprise there were hardly any studies on the cerebral impact of one of the most intense physiological experiences there is for humans.

How was that possible? How could there be dozens of manuals describing in detail how pregnancy affects every human system and organ but the brain? If sexual hormones play a key role in neuroplasticity, and if there’s no moment with bigger hormonal fluctuations than pregnancy, why had it never been studied in humans? Why weren’t scientists interested in whether there was biological proof that motherhood changes people as profoundly as women report? Sexual bias in biomedicine again?

But the biggest irony was that although we found hardly anything in PubMed, the rest of the internet was swarming with “educational” articles with titles such as “This Is What Happens to Your Brain When You Get Pregnant.” Evidently, mothers were getting bombarded by opinions based on scant scientific evidence.

Scientific knowledge about the maternal brain was at that point reliant on some of the rat and mouse studies we discussed in the previous chapter. In humans, the neuroscience of pregnancy and maternity was what we could ironically call a virgin field. It was almost untouched. We found a couple scattered nuggets of information that stimulated rather than satisfying our curiosity, such as a study that demonstrated that the hypophysis, also known as the pituitary gland, grows during pregnancy. Another looked at the brains of women who suffer from preeclampsia. 

The pituitary study has its origins at the end of the 19th century, when a doctor named Louis Comte observed enlarged hypophyses in six women who, sadly, had died during pregnancy or shortly after giving birth. Approximately a decade later, two other investigators, Jacob Erdheim and Emil Stumme, found that this growth was located in certain cells in the hypophysis whose job is to produce hormones and named them “pregnancy cells.” Other authors observed that the more pregnancies a woman had, the larger her hypophysis was, which suggested that these changes were both lasting and somehow accumulative. In the middle of the 20th century, Richard M. Bergland and collaborators discovered that the so-called “pregnancy cells” were actually neurons whose role is to produce, store and release prolactin into the bloodstream. According to them, these cells grow in both size and number. They’re now known not as “pregnancy cells” but as prolactin cells or lactotrophs. At the end of the 1980s, a group of scientists used MRI to calculate the percentage increase in this pea-shaped gland. José G. Gonzalez and colleagues estimated that by the end of pregnancy the hypophysis is 136 percent bigger than it was and that after birth it decreases progressively. The increase in the hypophysis’s size is clear enough that you can see it through an MRI scan without a microscope. If you’re curious, you can visit Neuromaternal’s Instagram account (@neuro.maternal), where there are videos of a hypophysis growing as its owner’s pregnancy advances.

The study about preeclampsia was published by the Imperial College School of Medicine researcher Angela Oatridge in 2002. In it, scientists evaluated the brains of women with preeclampsia as well as women experiencing healthy pregnancies who served as a control group. It was a very small sample: 5 women with preeclampsia, 11 without. Only two had had their brains imaged before getting pregnant as well as after birth. The rest were studied during pregnancy and after birth. The researchers found no differences between pregnant women with and without preeclampsia, but their results, especially in the control group, contained the hidden seed of what my colleagues and I were later able to demonstrate. We didn’t know it yet, but that article, which we skimmed in the fall of 2008 and which the scientific community had unjustly overlooked, would become a key reference point for us.

Excerpted from “A Mother’s Brain: The New Science of the Neuro-Maternal Revolution” by Susana Carmona. Reprinted with permission from the MIT Press. Copyright 2026.

Watch our conversation or read the transcript.