Susana Carmona, neuroscientist: “We know more about the universe than about women's brains”

Motherhood is an event that changes women's lives, but also affects—probably forever—their brains.

Susana Carmona (Terrassa, 43 years old) knows this very well, since together with her team from the Gregorio Marañón University Hospital (HGUGM) she signed the first study, eight years ago, on the neuroplasticity of this organ during pregnancy.

They discovered, among other things, that the gray matter of pregnant women is reduced in the months before and after childbirth, although the reasons and purposes of these changes remain a mystery that needs to be investigated in depth.

“The further we advance, the more we know about women's brains, but more and more questions also arise,” acknowledges the doctor in neuroscience, who leads the HGUGM Neuroimaging Group and has just published a new study on the matter.

Q.

Why does the brain of pregnant women change?

A.

The question is, how is the brain not going to change?

A woman's entire body changes during pregnancy.

Your cardiovascular system, your kidney system, your feet are going to grow, your skin color changes... It happens because all the organs have to adapt to gestate.

The difference is that, in some cases, we know directly the specific function of why it adapts, and in others we do not.

But what seems strange to me is that no one had asked what happens in the brain when a woman's entire body changes.

Q.

Why do you think no one asked this question?

A.

There is a sex bias in biomedicine that is very important, not only when we talk about pregnancy.

Menopause is also another great unknown, or the effects of hormonal treatments.

There are many girls who are taking contraceptives today, and there are still not enough studies to know what happens at the brain level.

We know more about the universe than about women's brains.

Q.

What exactly did you discover with that first study?

A.

The first thing that was discovered, and the reason why it had such an impact, is that a woman's brain changes profoundly with pregnancy.

And when I say deeply, I mean that I have been doing studies with different mental pathologies and analyzing brains for many years, and I have never seen changes as powerful, as marked and consistent as those that occur during pregnancy and motherhood.

We saw that a woman's brain changes and that the more it changes, the better the bond with the baby.

From there, many questions arose, which is what we are now investigating.

Q.

For example?

A.

People want to know what happens to fathers, if they also change like mothers.

Or if these changes are similar to those that occur during adolescence.

Since then we have not stopped investigating to answer all these questions.

In 2019 we published another study in which we compared the anatomical changes that occur in a woman's brain during pregnancy with those that occur in girls when they go through puberty, and we verified that at the level of shape and magnitude these changes are very similar. .

In both processes there is a decrease in gray matter.

Q.

Said like that it seems like something bad...

A.

Now, when you say that a woman's brain reduces in volume, everyone automatically thinks of degeneration, of atrophy.

But in biology less is not always worse.

To study these changes we use magnetic resonance imaging, which allows us to know what is happening at the brain level.

For now, we have not observed an association with cognitive changes, in what may be the way of executing tasks during and after pregnancy.

If we look at animal models, where there are more studies with mice, we see how neurons are more connected in some regions, while in others they are less connected.

Q.

What exactly does this mean?

A.

Right now we are not very clear about our hypothesis.

At first, since we saw changes similar to adolescence, we thought it was due to a mechanism similar to synaptic pruning [the process by which most of the unnecessary connections formed in the first years of life are eliminated].

Now we are not so clear, because the changes are very dynamic.

What we see is that some changes persist and others do not.

This is telling us that the cells that are behind these changes have to be very dynamic.

And we know that during pregnancy, the mother's entire immune system has to be hacked in order to tolerate a being that is genetically different from you.

The explanation could be this, but right now it is a hypothesis that we are investigating.

Q.

Is it possible that the change has the function of preparing the woman for care?

A.

It is what we want to discover, but to affirm it now would be philosophizing.

A study that we are working on with the team at the Autonomous University of Barcelona will soon be published that may give us certain clues, but I cannot give too much information yet.

What I can say is that it is not a direct relationship.

It is not the brain that changes to care, which is often what is misinterpreted in the results.

It is the way it has changed that has made you care, and the fact that you care has made the species survive as it is.

Q.

In the latest published study, they found differences depending on the type of delivery.

A.

This study was not specifically aimed at investigating the type of birth, but it has allowed us to obtain useful information in this regard.

We have had 12 women with a scheduled cesarean section, 11 with an emergency cesarean section and about 80 with a vaginal birth.

The comparisons are still preliminary to be able to give accurate answers, but by comparing the types of births we have seen that there is no difference between emergency cesarean section and vaginal birth.

The difference is between the scheduled cesarean section and the rest.

Because the hormonal environment that exists during childbirth, when contractions begin, has nothing to do with what happens during pregnancy or the postpartum period.

It is a unique situation that if not verified, as in the case of women who have a scheduled cesarean section, causes the brain to change differently.

Q.

Better or worse?

A.

It is early to say, and very dangerous, because it is not ready to be put into clinical practice.

It is something that we discovered throughout this study and that we have to deepen by controlling all the possible variables.

We have hypotheses as to why this happens, such as that childbirth itself already produces specific neuropathic effects.

Q.

One thing we do know for sure is that the more the brain changes, the stronger the bond between mother and baby.

As measured?

A.

It is very complicated.

The only way we have is to do neuroimaging studies and follow up with questionnaires.

These are questions that measure whether mothers develop hostility towards the baby, how much pleasure they feel when interacting with him... Scales that are validated and will give you a score.

What we saw in the first study is that brain changes predicted bonding after childbirth.

I do not believe that this association is direct, it must be mediated by other factors, and it is not absolute either.

It's not that if my brain doesn't change during pregnancy I won't have a bond with my baby.

Now, how do we go from brain, anatomy, brain to link?

Well, all these questions about whether there are hormonal factors that mediate them, immune factors, inflammatory factors, well-being, depression, anxiety, all of this is what we have to finish completing.

Q.

Can we talk about maternal instinct in neurobiology?

A.

It is very complicated for scientists to give names to things.

When you start looking for definitions of instinct, in every possible dictionary, there are subtleties that can make the answer yes or no.

For me, it's yes.

We can talk about maternal instinct, but with my mental definition of what maternal instinct is, which is not the desire to be a mother, or that suddenly you give birth and know what you have to do with the baby.

For me, the maternal instinct is a motivation to be in contact with the baby.

Not even enjoying contact with him, but worrying and being in contact with him to find out what's going on.

Furthermore, if this instinct did not exist, we would have become extinct.

Without the motivation to care, a thing that screams and often bothers, the human being as such would no longer exist.

Q.

How long do these changes in women's brains last?

A.

We don't know, but we have indications from other studies that they can be lifelong.

We have investigated what happens up to six years postpartum and changes are still seen.

But there are other researchers who take large databases, which have tens of thousands of participants, and compare those who have been mothers with those who have not.

There are already 70-year-old women in whom concrete changes persist.

It is also impossible to say exactly if biology is behind these changes or if the environment also influences them.

It may depend on the type of upbringing, or the lifestyle.

There are also studies that associate them with the hormonal levels of estrogen to which women are subjected during the nine months of pregnancy, and that in the long term could affect how the woman faces menopause and how she transitions to adulthood. .

Carmona works in his office at the Gregorio Marañón Hospital, where he leads the Neuroimaging Group.

INMA FLORES

Q.

And what happens with the following pregnancies?

A.

This is what we are investigating now, together with possible changes in the parents' brains.

But a lot of data is needed to draw conclusions, it is work that takes time.

Q.

Is it difficult to find participants?

A.

It is very difficult, especially depending on the approach of the study.

We need to monitor women before they become pregnant and then during the early postpartum period.

You have to do a lot of MRIs, but not all of them are going to be useful because many women who start the study are not going to get pregnant.

Others may lose the baby, or simply stop being interested, because it is a follow-up that lasts many months.

Also on an economic level it is very expensive, researchers have to be very motivated to want to invest their time in projects that take much longer than what science in Spain allows.

Q.

Besides researching a topic about which very little is known, what is this knowledge used for?

A.

Several things.

If we take it to the clinical field, the first thing that comes to everyone's mind is postpartum mental pathology.

Today we are trying to predict, treat and cure postpartum mental pathologies and we do not even know exactly what happens in a woman's brain during pregnancy.

So, one of the most direct applications would be to try to develop treatments aimed at perinatal pathologies.

Understanding how this may affect menopause, or how it may affect women who are at higher risk for Alzheimer's, is also important.

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