MRIs Show How The Brain Changes During Pregnancy

KATHLEEN DAVIS: This is Science Friday. I’m Kathleen Davis. Pregnancy is a hugely transformative experience, both in life and in the body. But there’s a key part of the body that’s been pretty under-researched in relation to pregnancy, and that’s the brain. If you’ve been pregnant, you may have noticed differences in your own brain.

Last month, a study in the journal, Nature Neuroscience, outlined transformative changes that happen in the brain during pregnancy. And here with me to explain these changes and what they might mean is my guest, Dr. Liz Chrastil, associate professor of neurobiology and behavior at the University of California, Irvine. Welcome to Science Friday.

LIZ CHRASTIL: Thanks for having me, Kathleen.

KATHLEEN DAVIS: So this research, it’s my understanding, is very near and dear to your heart because it wasn’t just any pregnant brain that was being studied, it was yours, right?

LIZ CHRASTIL: Right. I was studying my own brain. So I was working with Emily Jacobs, my collaborator, and her student, Laura Pritchard, who had just finished a menstrual cycle study. And we were working on menopause and other ways. But then I was planning a pregnancy. And so we said, hey, we gotta do this.

So that’s how it sort of started. And we went from there, and it was really exciting to be your own participant in your own study.

KATHLEEN DAVIS: And it sounds like this is a really understudied part of pregnancy research, studying the actual brain?

LIZ CHRASTIL: Exactly. We had almost no information about the human brain and what happens during pregnancy. There have been a few studies looking at before and after, testing people before they got pregnant and then what their brains look like after pregnancy. But we were really missing during. And so we had really almost no idea what was going to happen to the human brain, while pregnancy was ongoing.

KATHLEEN DAVIS: And so what were you really hoping to pinpoint here?

LIZ CHRASTIL: We were hoping to look at understanding more about what was happening, again, during pregnancy. We were looking at a couple of key features, so we were looking at brain structure, mainly focusing on the structure of the brain and how it might change.

So we were looking at volume, like sizes, and the strength of the connections and the quality of the brain connections. So we’re looking at gray matter, which is the cell bodies of the neurons, and we’re looking at volume of gray matter in certain areas like the hippocampus, which is important for learning and memory. And it’s important for when people have something like brain fog, that might be part of it, so we’re looking there.

We’re looking at cortical thickness, which again, is sort of volume across the brain. And then we were looking at white matter, which are the axons of the neurons, which are the connections between neurons. And those are these big fiber tracts that go across the brain.

And we were looking at the health of those connectivity and how well the connections are. And so we think of white matter as a road, and you want your road to be. Well paved. So we were looking at the quality of those connections there.

KATHLEEN DAVIS: And so as the central test subject in this project, what sort of tests did you actually run yourself through to find out the answers to these things?

LIZ CHRASTIL: So we did MRI scanning, and so the scans did several structural scans, looking at those volumes that I was talking about, diffusion imaging, which looks at the white matter. We have a couple other ones that we did as well. But it was about a half hour scan, 45 minutes each time and just went in there and did a blood draw as well so that we could also connect it with sex hormones.

KATHLEEN DAVIS: What is it like to be at the center of a study that you’re actually doing research on? Was that a little bit of like– no pun intended– was that a little bit of like a cognitive challenge for you?

LIZ CHRASTIL: It was OK. It was exciting, I think, more than anything, because, again, we were just forging new territory. And so it was sort of like we knew we needed a neuroscientist to do this study, almost because knowing what it takes to do these MRI scans, of course, I’ve done tons of MRI scans in the past just because that’s what we my research is about. And so being able to know what it takes to do this and what it might be involved with was part of it.

And so it was just more exciting than anything. And we never really looked at the data until it was done. And so that was another thing that was helpful, I think, because I didn’t see my brain changing in real time at any time. So we never wanted to affect anything with the study while it was going on, and so we didn’t look at it until well after.

So I just kind of was going in and hoping everything was fine, but essentially, not looking at how things were changing.

KATHLEEN DAVIS: Right. I would imagine if you’re actually looking at scans in real time and seeing, oh wow, things are really changing in there, that might be a little disorienting.

LIZ CHRASTIL: Right, exactly. And we had expected, for sure, some changes. And again, looking at the pre and post studies, we had expected some decreases in gray matter volume. So it wouldn’t be totally surprising, but we still did want to do it in time.

KATHLEEN DAVIS: So tell me. Exactly what you found.

LIZ CHRASTIL: So we found, overall, this decrease in gray matter volume and cortical thickness across the board of about 4%, which is not that big, but that’s a sizable amount when you’re thinking about your brain. And there was some variability, so some actually increased a little bit. Some went down by as much as 13%. But overall, the average was about 4% brain reduction in volume from before and after, and that was pretty much a linear trend. So we just kept going down.

We did, also, some postpartum scans, so several scans after pregnancy and then about six months and a year and two years out. And so that gray matter volume rebounded a little bit, but it mostly stayed the same. And then it kind of kept the same level for the two years out.

Then we also found in the white matter this really interesting nonlinear relationship. So what we found was an increase in the white matter, connectivity integrity that peaked around the second to third trimester, and then it went back to baseline by the time the baby was born. And so that had this sort of interesting peak and then return of integrity that we wouldn’t have seen if we had just done a before-and-after design.

So if we had just done before and after, we would have completely missed that part. And so this was a really new and interesting finding that we were able to discover.

KATHLEEN DAVIS: In general, what do we know about gray matter, white matter, and what they actually do in the brain, like what their purpose is?

LIZ CHRASTIL: Yeah. So gray matter are the cell bodies. And so we think that a reduction in gray matter might be worse. So when you think about it, you’re like, your brain shrinks. That doesn’t sound so great. But there’s a lot of things that are going on there. So there are pruning. And it could be the amount of dendritic spines, which are the connections between each neuron at the synapse.

And so that’s one possibility in terms of the reduction, and that might not be a bad thing. So in adolescence, there’s a similar reduction in volume during the adolescence and puberty time. And so it’s not necessarily a problem.

We also see this during childhood that there can be changes in connectivity and pruning and things like that. So reductions in volume are not necessarily a bad thing. But we don’t necessarily know, again, what the actual cellular mechanisms are for this reduction in volume. And likewise, we don’t necessarily know what the cellular mechanisms are for the increase in white matter integrity. We need some more animal studies to do that.

But what we can say is, again, that we do see the quality of the connections. So the white matter is, again, like this sort of tube that runs across your brain are connecting broad areas or straw. Sometimes we think about that. So we’re looking at the diffusion of water in the white matter.

And so it looks like the diffusion is happening. There’s less diffusion in the sense that it’s going more like it’s going through a straw, which is what you want. You want it to be more like it’s going through the straw and better road paving, again, for your white matter.

So these are how your neurons are connecting to each other and how their volume is happening. And so again, what we need to know now that we have some of this information is to go into either in vitro studies or animal studies and to understand more about what are those particular dynamics happening on the cellular level. So we’re looking at a scale that’s a little harder for us to see at this point.

KATHLEEN DAVIS: I know that you study behavior. At this point, is there anything we can glean about how these differences in gray matter and white matter might actually change our behavior in pregnancy?

LIZ CHRASTIL: That’s the big question that we want to find out. So we know a little bit about behavior. So we know from animals that if you give animals who have never had any pups, if you give them some of these hormones, that they will now have some changes in their maternal behavior and grooming behavior and caregiving behavior and things like that. So we know that there are some, certainly, aspects of this.

We know from another study, from that Susanna Carmona study that looked at before and after in humans that some of the relationship with the volume reduction that they saw was related to some social interactions recognizing your infants and a little bit of maternal care. So we think that there’s some relationship, but we still don’t really know what it means. And so that’s the big question that we want to move forward with, is understanding does it mean anything for care? Does it mean anything for things like brain fog or thinking or anything like that?

So I didn’t actually experience any brain fog when I was pregnant as far as I remember, so I didn’t really have that experience. But a lot of people do, and so we want to know more about what’s going to likely happen in terms of these changes in the brain, and are they going to be affecting people’s behavior.

KATHLEEN DAVIS: Yeah, I want to ask you about brain fog, because I’ve heard this term pregnancy brain referred to a lot by people in my life over the years. And this idea that there’s brain fog and maybe forgetfulness that happens during and after pregnancy.

We even got a message from listener, Chris, in Traverse City who said that they could feel their IQ drop when they were pregnant. I think there’s maybe a little bit of a joke in there, but could this idea of pregnancy brain be connected to these changes, and what do we need to study to know if that’s the truth?

LIZ CHRASTIL: So it’s certainly possible. And so that’s, again, what we need to find out. And so there’s a lot of things that can contribute to a pregnancy brain, this feeling. So what we don’t know exactly is where it’s stemming from. So you’re not sleeping as much or sleeping as well, certainly during pregnancy, but of course well after pregnancy.

You’re stressed out. You’re worried. Lots of things like that. You’re starting to take care of another human being. You have to manage all these other things. So there’s a lot of things that can be going on, both during and after pregnancy that we can attribute this to.

And so it’s hard to know exactly if it’s specific to the brain structure, if it’s more about sleep, if it’s more about stress or other things. And so that’s what we need to find out more with. So one thing that we’re really interested in looking at next is some of these behaviors and thinking about both cognition in terms of pregnancy brain and thinking. We’re also really interested in thinking about postpartum depression and peripartum depression.

So a lot of people, again, experience these depressive symptoms, and we want to know if the structure is important for that. And so is it anything that’s happening during pregnancy? Is that predictive of postpartum depression? Is it after pregnancy? Is it something else? And so understanding more about that is going to be really informative.

There’s lots of other things that might be important too, things like pre-eclampsia, which is really more like high blood pressure, but that’s a vascular issue that’s going to affect your brain. And there might be signatures of pre-eclampsia in the brain and that might also have long-term health implications. And so again, that can be really important as we move forward.

So I think there’s a lot of open questions here. And this research, I think, really opens more questions than it answers, and so we’re excited about it.

KATHLEEN DAVIS: It makes me wonder if these changes in the brain during pregnancy is one of those things that developed in evolution and it has some sort of importance, but we just might not know what it is yet.

LIZ CHRASTIL: Exactly. And so that’s my take on it is that we’ve had millions of years of evolution. And this is probably adaptive in some way, but we don’t necessarily know what way that is adaptive. So it’s almost certainly going to be helpful, but is it a trade off with other things. So because your body is changing all these other systems that are going on, and there’s certain energy requirements, right.

So is it going to be a trade off with other things, or is it enhancing? Again, likely to be maternal care or other things, but maybe not. And so figuring out where it’s adaptive and then where it’s maladaptive. So when it goes wrong and someone gets postpartum depression or something else, where is that happening, and how can we detect that and figure out ways to detect and treat that.

KATHLEEN DAVIS: So to me, it’s a little staggering that this type of research hasn’t been done before, considering how many pregnancies happen all the time. When you got pregnant, were you like– OK, if no one else can to do this work, I’m just going to do it on myself, on my own terms.

LIZ CHRASTIL: Yeah, pretty much. Exactly. So we knew that it needed a neuroscientist to do this. And so I’ve done MRI scans many times in my life just because that’s what we do. And so being able to know what it takes to do this and to set this up and to make it happen was needed.

And yeah, it really is just shocking. I mean, the paper, again, opens more questions than it answers. And so the fact that we ask this question is why we’re getting so much so much response, because people want to know and no one has bothered to find out. And so that’s where I think there’s a lot open things to talk about.

And it’s really, again, shocking. It’s 2024, and we know so little about what goes on during pregnancy and generally, in the female brain and other things. So again, thinking about menopause, that’s another area that we’re really interested in. And again, very little is known about that. I think there’s a little bit more there, but, historically, women’s brain health has been understudied. And so that’s something that really needs to have a change in understanding and approach to think about that.

KATHLEEN DAVIS: Did, actually, having this pregnancy experience bring up other questions that you want to know the answer to? Being pregnant while working on this study, I mean, are there other things that came up that maybe you weren’t expecting to?

LIZ CHRASTIL: Yeah, well, I think, for sure. Certainly, I didn’t necessarily know what to expect, what sorts of things would happen. Yeah, so I wasn’t sure whether I would have any brain fog symptoms, and I didn’t but I could have, and that might have had certain implications.

Just trying to understand more about comfort levels and things like that, trying to understand more about sort of planning and all the stress and things like that were definitely something that I would like to be able to do more. And then support systems, I think, as well afterwards. I think that’s a big important question that should be studied more, and we didn’t get a chance to look at that.

KATHLEEN DAVIS: So we’ve talked a lot about the unknowns that still exist around this topic. But now, that we have this first round of information, we have this map. I mean, what would you really love to learn next?

LIZ CHRASTIL: I’d really love to learn how this relates to your brain function. And so, again, this was all structure. And so understanding more about the functioning of your brain would be a really important question and then how that relates more to behavior and behavior very broadly. So again, memory, attention, depression, all those sorts of things, I think they’re all open.

KATHLEEN DAVIS: Well, that is all the time that we have for now. I would love to thank my guest, Dr. Liz Chrastil, associate professor of neurobiology and behavior, at the University of California, Irvine. Thanks so much for joining us.

LIZ CHRASTIL: Thanks for having me, Kathleen.

KATHLEEN DAVIS: And one more thing before we head to the break, we need you for just a couple of minutes. Yes, you. We’re surveying listeners to our radio show and our podcast, the folks who attend live or virtual events, those of you who follow us on social media, who are dedicated to our book club, we want to hear from all of you, no matter how you enjoy Science Friday.

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After the break, how a grain called kernza is making its way into food and drinks. We’ll talk about what this grain is and its benefits for the soil.

SPEAKER: When we’re looking for crops that both feed people, but also, help mitigate some of the effects of people on the planet, something like this long-lived relative of wheat is really appealing. And I’ll just mention, this is one of thousands of species.

KATHLEEN DAVIS: Stay with us.

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