Susana Carmona: “Motherhood rejuvenates the brain”

Pregnancy is a unique moment. So much so that women’s brains change. This metamorphosis was known by popular knowledge, but since 2017 it has been scientifically proven. It was achieved by the neuroscientist Susana Carmona (Terrassa, 1980), Director of the Neuromaternal neuroimaging research group at the Gregorio Marañón Hospital and Co-principal investigator of Group G-07 of the Mental Health CIBER of (Carlos III) and her team, eminently female. She has now captured part of the findings in Neuromaternal (Penguin Random). Carmona, a researcher trained at the UAB, Columbia and Harvard and mother of an eight-year-old girl, believes that the best studies are born from her personal motivation, and this is the result of “stubbornness” without funding and with many overtime hours. Now they are trying to put together the puzzle to continue answering questions about the female brain that have yet to be answered because “gender bias in biomedicine” has historically forgotten to investigate women.

How does a pregnant woman’s brain change?

We have observed reductions in the volume of gray matter, which is where the body of neurons and also other brain cells is located. These reductions appear to peak around childbirth and then reverse slightly in some regions and in others appear to persist for years if not for life.

In which regions does it not revert?

In those regions involved with the default network. This network is the one that human beings activate by default, when they ask us not to think about anything and our mind begins to wander. It is related to the perception of self, and we use it to infer the emotional and mental states of others, to empathize with them.

Does the brain get smaller?

Reduces the volume of gray matter. What happens at the cellular level, we don’t know. But we know that a reduction in volume does not necessarily imply atrophy or a decrease because something similar occurs during adolescence.

A priori, talking about reduction is scary…

Clear. People associate volume reduction with dysfunction, atrophy, alteration, deficit… but this is not always the case. In adolescence we talk about synaptic pruning. During childhood, connections are overproduced, everything connects with everything, later, in adolescence, the brain begins pruning, eliminating connections, to optimize processing routes. The transmission of information goes through more optimal routes. We do not know if the same thing happens during motherhood, but one possibility is that it is a similar process.

From what moment does a pregnant woman’s brain change?

We now have an article in review and I can’t talk too much about it. But we know that it happens before childbirth. In the third trimester, the mother’s brain has changed profoundly.

With birth, is a new woman born?

Yes. There are many popular phrases that talk about that. Almost all mothers tell you that they feel different after motherhood. It is something that classic authors in psychology already talked about. What we have done is put it into scientific language and demonstrate it with brain images and very robust statistical values ​​that leave no room for discussion. Only with the image of the change between before and after the first pregnancy can we know if a woman has gone through a pregnancy.

Are there women in whom these changes do not occur? What happens if they don’t change?

The changes are so powerful that they occur in almost all women to a greater or lesser extent. Now we are trying to explore what makes some change more than others. Maybe the hormonal values… And we don’t know what consequences there may be if there are no brain changes. We know that the more the brain changes, the better the link. But it doesn’t mean that if it doesn’t change there won’t be a connection.

At what stage do they begin to study them?

Before getting pregnant for the first time. We evaluate them at that moment and later either during pregnancy or in the postpartum.

And until when?

In some studies we have up to six years postpartum. But they are longitudinal studies, very time-consuming. We are in different international initiatives, some led by the United States. Our idea is to add data from different world institutions to be able to provide a long-term response.

Do brain changes persist at six years old?

Yes. In the study published in 2020 we saw changes that persisted six years later. But there are other European researchers who have compared the brains of thousands of middle-aged women, some of whom were mothers decades ago. They observed that the brains of those who were mothers were different from those who were not. Some women in the sample were 70 years old. So it seems that many of the changes are lifelong.

What kind of changes?

These researchers used an algorithm that allows you to predict the age of the brain. They observed that when they tried to predict the brains of women who had gone through pregnancies, the algorithm’s prediction was younger than for those who had not been mothers. It predicted a younger brain age. The scientific community proposes different hypotheses to explain the results. One is more biological and says that the hormones and immune adaptations of pregnancy seem to cause women to enter menopause in a less inflammatory state and that would make them reach old age with a “younger brain.” And another hypothesis more focused on lifestyle: being a mother entails a series of variables that make a woman arrive younger. For example, you have to train a lot of cognitive skills to be able to function taking care of a baby and in a work environment. You have to train your brain constantly for many years, learn to regulate your emotions, plan, be mentally flexible… Then when the baby is older, the brain has already been trained for many years and means that you reach old age with more resources, with greater cognitive reserve. They are the two hypotheses, simplifying a lot.

Motherhood is a time of stress.

Without a doubt, a pregnancy is taking the body to an extreme and in the body is the brain. The stress of being a mother and the effort you have to put in is brutal. But precisely for that reason, because you are functioning at very high levels, this generates a series of resources that help to better manage the environment. The problem is when too much is asked of us. Could we say that motherhood rejuvenates the brain? According to these studies, which are not ours but are several and published in very important journals in the field, yes. The more children you have, the younger your brain is up to a certain limit.

With a second pregnancy are there new changes?

We are now investigating that. The study of the human maternal brain is something super novel. We published the first study in 2017 but, luckily, we have a lot of data from animal models. There are 50 years of research on rats, which are also placental mammals, and from there we can extrapolate certain things. Pregnancy hormones modify the animal’s brain to facilitate maternal behavior. We also know that these changes occur especially during the first pregnancy and that it is much easier to implement maternal behavior in subsequent pregnancies… The main changes occur in the first pregnancy and then they are readjusted. And from these studies we know that these are lifelong changes. If we look at what comes from animal models, everything indicates that the most powerful change occurs with the first pregnancy, but we still have to prove or disprove it empirically in humans.

Are these changes only attributable to biological motherhood?

No. From animal models we know that what gestation hormones do is change the brain so that it behaves maternally quickly, at minute 0. Because the baby needs to be taken care of now. But we also know that there is a period of awareness. In rats that have not gone through pregnancy, in male rats, brain changes also occur with mere exposure to offspring for a long time. In this case they are influenced by the interaction with the baby. We believe something similar happens in humans. We are now doing studies on adoptive mothers. To date, there are no studies that compare the brains of women before and after their first adoption.

So does the brain of the father or the surrogate’s partner also change?

We can say “yes, but”. The changes we see in pregnant mothers are much more pronounced, of a very different order of magnitude from those seen in fathers and we assume also in non-pregnant mothers. At least at the time we measure it, which is early postpartum. Maybe after two years things change. Parents’ brains change, but less. And some don’t change. We think it depends on the interaction with the baby.

Before, I don’t know you gave importance to what happens after giving birth. Was childbirth seen as the end of everything?

Because “the product” was the baby. In women, pregnancy has always been studied from the neck down, something absurd because all the hormones secreted by the placenta alter all the organs and can reach the brain and if they alter all the organs, how could they not alter the brain?

He declares himself a fan of the placenta.

I’m discovering it as I go. It amazes me how an organ that has an expiration date can orchestrate or hack a system so that a human being can create another with his own body. And I am very fascinated by the adaptation of the immune system. Pregnancy is so common that we take it for granted that everything works because it has to work, but it is curious to stop and think that our entire immune system is designed to detect and attack any organism that has different genetics than ours. With the arrival of the baby, thanks to the role of the placenta and the substances it secretes, not only does it not attack it but it starts working for it, to optimize pregnancy and childbirth. Make the organs communicate differently with each other…

Depending on the type of birth, are the changes that occur different?

Yes. It is a result that we found by chance in our last study. We looked at the brain before and after giving birth. We thought that perhaps there were differences between cesarean delivery or vaginal delivery, but we saw that the difference depended on whether they had gone into labor or not. That is, scheduled cesarean section or start of labor. If the hypothesis is that brain changes are produced by the immune system and hormones, what happens in the process of giving birth is a different hormonal and immune cocktail. Pregnancy, childbirth and postpartum, which are sometimes put in the same package, involve different changes at the immune, hormonal, environmental and, now we have shown, also brain levels.

We are beginning to learn about women’s brains, which are still largely unknown.

Yes. It had been excluded many times from scientific studies. The brain is an endocrine organ, it has hormone receptors: it emits hormones to the rest of the body and receives them to adapt its function and anatomy. The body of XX women who are born with ovaries is subject to a menstrual cycle with a series of fluctuations in estrogen and progesterone, hormones that cross the blood-brain barrier, bind to receptors and have been shown to induce different mechanisms of brain plasticity. As many times women have been excluded from studies precisely because it was thought that the issue of hormones complicated everything and they studied the “standard” human; to the man. Now there is a very powerful movement that tries to reverse this sex bias so that there are the same studies or so that the sex and gender variable sheds a little light on us to reach personalized medicine, which is the objective of all medicines.

Are there brain changes during menstruation and menopause?

Yes. In these international initiatives, we lead the pregnancy and maternity part. But there are other groups that lead menopause and another on menstruation. You look at the course of a woman’s life and the periods in which she is at greatest risk of suffering from a mental disorder coincide with these periods of large hormonal increases. Hormones that we know can cross the blood-brain barrier and that have receptors in the brain in regions involved in the regulation of emotions, in cognition… Menopause was a great unknown and studies are currently being published that I hope can help us. It is something that has been ignored for so long and all women are going to go through it with a little luck and it has so many symptoms, not only bodily but also cerebral, mental, psychological. It is important that we pay attention and be able to treat it appropriately. Pregnancy affects a high percentage of women, but menopause or the menstrual cycle? We’re all going to go through there.