You've probably heard the term pregnancy brain or baby brain.

I have baby brain. I'm like in a different world. I don't know what day of the week it is, to be honest.

It's a phrase that's often used to mean that someone is kind of scattered or unfocused.

I love baby brain. I mean, I don't know exactly, I'm not a scientist, but supposedly so that moms focus on their baby, you can't really think of other stuff. And it's true, because I can't think of anything else.

That's Kourtney Kardashian, and you know what? She's probably on to something. Because the brain isn't static, even though we often think it is. Our brains are changing, and they change throughout our lives, especially women's brains. They change during the three P's, puberty, pregnancy, and perimenopause. Now for women, these transitions aren't just happening in the body, they are happening in the brain as well. That's a really important point. And it's exactly what cognitive neuroscientist, Dr. Laura Pritschet, studies, how the brain actually changes across the many phases of a woman's life.

And the reason I chose that field is because I was a budding neuroscientist as an undergrad interested in brain networks and obsessing over how intricate everything was in the brain to simply allow us to have a personality or remember things. At the same time, in my personal life, I was surrounded by menopausal women who were talking about their cognitive complaints and their attention issues, specifically in that time. And I thought, we've got to connect these two together and understand this more.

'Dr. Pritschet recently published the first-ever longitudinal study, meaning that she actually followed the same person over a long period of time, specifically tracking the brain before, during, and after pregnancy. Not just in a few snapshots, but in these dense, detailed scans that then continued two years after the birth of the baby.

It showcases this choreographed dance between major features of our brain that are changing over pregnancy itself, which in theory can underlie this sort of preparation for the next stage, which is parenting, caregiving, motherhood.

So I wanted to talk to her about how and why brains change during pregnancy and what those changes might really mean for parenthood and even beyond. I'm Dr. Sanjay Gupta, CNN's chief medical correspondent. And this is Chasing Life.

Was there a specific question that you were trying to answer or were you just trying to establish that there was variations that occurred throughout that time period?

'We've begun shedding light on how the brain reorganizes in response to pregnancy. It's a transformative period in a person's life. It's tied to hormonal change, social change, environmental change. But what changes happen during gestation itself? We're missing huge gaps in what we call this sort of metamorphosis. We know that the 40-week gestational window leads to these body adaptations to support the development of the fetus. We have increased plasma volume, immune function change, metabolic rate, oxygen consumption, but we don't know what that looks like. So the question was what does this trajectory look like over gestation and was also the sort of proof of concept to say stuff is changing and we need to study this at length. And so that's what we sought to do just starting with one person. But yeah, that was what we did, this intensive longitudinal design over a single individual who is scanned preconception, during IVF, along all three trimesters into two years postpartum.

And you noticed objective changes in the brain. Gray matter thickening or thinning, did you say?

'So our findings, which looked at a woman's brain pre-peri-postpartum, found that as women advanced through their gestational weeks, zero to 40 weeks, we saw this reduction in gray matter volume pretty much across the whole brain that was also shown if you look at cortical thinning. We saw increased white matter microstructure and ventricle size.

'Okay, let's take a quick step back here. The brain is made up of gray matter and white matter. Now gray matter is where most of the brain's thinking and processing happens. White matter helps connect those areas. Think of it like the wires that let different parts of the brain talk to each other. So when Laura talks about changes in gray matter and white-matter microstructure, she's talking about real physical shifts in how the brain is organized. And possibly how it might function during and after pregnancy.

You know, the inflection point was birth, and we saw that those reductions persisted into postpartum with slight recovery, meaning that certain areas of the brain showed this rise in gray matter volume in the early postpartium, others did not, but it showcases this choreographed dance between major features of our brain that are changing over pregnancy itself, which in theory can underlie this sort of preparation for the next stage, which is parenting, caregiving, motherhood.

'In this one patient, at least even during the IVF cycle, during pregnancy, and then postpartum, you said maybe there was some recovery back to sort of pre-pregnancy brain structures. How far out did you look?

We studied her up until two years postpartum. We studied and scanned her brain a lot more in the early postpartums. So we have fewer data points one to two years out. But you can look at that trend and you see there's a little bit of partial volume recovery, but it never really goes back to baseline for the gray matter volume.

'It's interesting because as you point out, so if people who are listening can just imagine the brain and you know people think of brain as gray matter but it's gray matter and white matter. You have gray matter sort of on the outside, you have these white matter tracks deep within the brain. You may have gray-matter what are called nuclei, so these sort of very important areas deep in the center of the brain, you are describing a picture where gray matter sort of shrinks, more so sounds like around the edge, the cortex as it's called. But when that happens, if the volume stays the same, some of those white matter tracks may expand a bit. Some of the natural fluid-filled spaces in the brain may expand a bit to maintain that overall volume. That's the picture you've described as what happens during pregnancy in the brain. Again, not to oversimplify, but is this a good thing or a bad thing?

'Yeah. So when you hear shrink or like a reduction of volume, right? Most people are going to say, oh, that's not good. And it's a self-fulfilling prophecy. If I've learned anything from talking to people about this paper is, oh yeah, like I could have told you that my brain is shrinking. But in reality, there's likely two things that are going on. One is there's this physiological adaptation to pregnancy itself. So there is going to be some swelling, some cortical pressure, where there's increased blood flow. All of that. And our brain, just like our placenta, our belly, our feet, all of it is gonna be adjusting to meet those demands. Some things will go back to baseline when you don't have that fluid retention. The other thing is, and this is based on evidence not just from our paper, but from everyone in the field that's leading this work is that it's a fine tuning of circuits. We know that pregnancy is the lead up to this time in your life where there's a lot of behavioral adaptation that has to occur. And a new cognitive demands and a new cognitive load. And so the idea here is that there is this pruning or this delicate rewiring to make certain networks or to make communication in the brain more efficient, to meet the demands that are going to have to occur. And interestingly, we see the exact same pattern in other periods of brain development, like adolescence, right? Adolescence is marked by this onset of hormones and puberty. We see this fine-tuning, gray matter volume reduction, increased white matter and white matter microstructure, a suite of adaptations that have to occur, cognitive mood, behavior changes. But it's specifically, I think, with pregnancy because there is a lot of subjective and sometimes objective changes in cognition. We really tie those changes to like, oh yeah, they're harmful. But in fact, we zoom out and we look at the lifespan. It actually can be beneficial that this is happening. And this is very normal. So don't have to think of it in the sense that there's reduction, so my brain is shrinking and I can't function. And in fact, it's good that this is happening.

Pregnancy brain and I don't know if that's considered a pejorative term if it is I apologize to anybody. But you know being more forgetful, you know things like that, does that translate to being a better mom, I mean like how do you how do your correlate those two things?

That's an interesting way to phrase it. And I do think people are trying to rebrand mommy brain or pregnancy brain, albeit that's what the common terms are. So that is interesting because, for a couple of reasons, one is the first sort of pinnacle papers that came out looking at neuroanatomy in human women from preconception to postpartum found that degree of change in gray matter volume, that sort of reduction correlated with various maternal care or maternal behavior. Again, that's all correlation—

What does that mean? Like what though? Because again, you know, your memory centers are sort of in, you know, you're hippocampus or these certain areas of the brain. With cortical fitting, what did that translate to in terms of what the women were experiencing?

Yeah. So what they found was that reductions in gray matter volume, especially in regions that overlap with theory of mind that are important in caregiving and all of that, emotional processing, higher order cognition, if those areas that changed the greatest, so they had the greatest decline in gray metal volume, which again can be a fine tuning, showed positive associations with bonding with their infant. And they also showed that sort of there was less hostility to their infant. Again, that's an area we need to do a lot more research on, and it needs a lot of context, because any time you're about to say, the more forgetful you are, or that you're brain changing, maybe that's out of your control, is gonna predict how good of a mom you are. It's like, just a, like, I don't think we can actually answer that at all, but it is, the overarching question is like, how can we tangibly contextualize that gray matter change? But you can expect that if there's fine tuning in these circuits that underlie sort of cognitive or behavioral process that the more fine tuning and it goes, the better performance you're gonna have. That's the idea, but it's so much more complicated than that. But yeah, there are people who are looking at the degree of cognitive change in relation to how their postpartum experiences are. Now those that are struggling the most that maybe have the greatest degree of cognitive complaints or feel those cognitive change, could be those people that are the most vulnerable to a lot of things that occur in postpartum too, including mood disorders or sleep dysregulation and don't have that support. And all of that compounds your relationship to your offspring, and that's why we need to have as much support in the postpartums as possible.

Okay, after the break, we've talked about how the brain shrinks during pregnancy, but I think the next question is, what happens after that? We're going to dig into how these changes could sharpen social instincts, help people tune into a baby's needs, and also answer the question of what this might all mean for your brain long after the diapers are gone.

So just for the audience, because we're using a lot of neuroscience terms here, you know, talking about cortical thickening and of changes, obviously, in the brain as a result of pregnancy, what do you think the message is there for people?

'I think where I always start is that this is a critical period of brain development and there's going to be this period of neuroplasticity, our ability to adapt to physiological and environmental demands where we can ease up on the inhibition and change things as necessary and that's normal and that is really cool and just as you would expect every other part of your body to change, so is pregnancy. And it's not necessarily a bad thing, but it's a window of opportunity to maybe fine-tune certain circuits, it's also a window of vulnerability. Anytime your brain is in flux or you're in a transition stage, there's going to be vulnerability to, say, mood disorders or neurological-related conditions that we can get into as well. But it's just almost a way to provide quantitative evidence for all of the things that women have been feeling for time and time again, that there's this choreographed dance that's occurring between your gray and your white matter over this gestational period. Ultimately to prepare you or to be able to adapt to all of the demands that are happening now or happening in the future.

This should be reassuring, it sounds like, to some extent.

Yeah, I think so. And from the people I've spoken to, it's helped them understand a little bit more of why things are happening. And I think anytime you provide evidence that this is occurring, and it can fit within them saying, yeah, if you talk to any person who's gone through pregnancy or parenthood, they're going to say, yeah like my brain feels different now. Like my auditory cortex has to have changed because I hear things differently now. And so to be able to say like, look, that's that region over this gestational period changing is I think reassuring and hopefully interesting. And if we show that and tie it to this message of this is adaptation and it's not this sort of shrinking but rather like this shift, this metamorphosis, this etching, however we wanna package it, it's a really powerful and cool thing that's happening for a reason. And to mostly everyone.

And that reason fundamentally, I mean, and again, I am very careful as a fellow neuroscientist not to oversimplify, but the reason that these brain changes happen, could you make the case that it's to better prepare you, equip you to care for this child?

That's a leading theory for sure. And I think you have to ask the question of like, anytime that your brain is gonna undergo change like this, it takes a lot of energy and it's resource heavy. And so why would we be doing that if it wasn't for some sort of reason? And pregnancy itself is a central facet of reproductive life that's how we, you know, it's happening ubiquitously across women and 85% of women are gonna experience this.

It does raise this question as well about whether you did, I don't know how old the woman was that you originally did the study on, but would it make a difference for women who are older when they have their children?

'Yes, this was just almost a proof of concept study to say we haven't been doing this and there are a variety of reasons why, but we need to ask this and here are a ton of low hanging fruit. So one is the age component. So our subject was 37. And if you hear, I always like to start my lectures or talks with what comes to mind when you hear brain development. And it's always, oh, it's, you know, in utero or infant or adolescent brains. And it really is like the first couple of decades of life. And then I always hear that like 25, your brain is done developing. And then, I showcase this data and I'm like, this is a 37 year old female who look at her trajectories of the brain compared to adolescence. But it opens up and the reason I'm saying that is because another huge question then is, okay, what if you undergo pregnancy at 20 or 18? When there are other sorts of periods of brain development occurring or 40 or 45, how does that influence your menopause trajectory? How does that influenced brain health later on? We don't know. We also have no real idea of what these changes look like in a second or a third pregnancy. If that second pregnancy happens one year later or five years later, low-hanging fruit that we just have not mapped.

It's fascinating. So the person you followed through pregnancy was 37 years old. Everyone is different. And you mentioned this at the top, Laura, but how you want to reproduce these findings, obviously, that's the nature of science. So what can we say at this point? How valid do you think the study is in terms of what this means for brain changes and pregnancy overall?

Yes, so I feel very confident in having spoken to all of my colleagues and all of the pioneers in this field that one of the most consistent findings in neuroscience is this sort of persistent reduction and this that persistent reduction.

Persistent reduction in gray matter and cortical thickness.

Exactly. We see this in about, because other people have looked at this and measured this, maybe not in the way we did, but this sort of snapshot or one or two times during pregnancy now is coming online. And it's just consistent. Like 90% of and above of participants are showing this. We have prelim data from the people who've followed up and done this exact protocol that show nearly the same patterns. And we have all of the translational research too. One, that pregnancy is a period of brain plasticity, and it's a critical window for brain change. And two, that you're gonna see this persistent reduction in gray matter volume and cortical thickness. The white matter microstructure finding that we saw is actually quite interesting because we saw this sort of nonlinear rise, and it said the measure of diffusion along that myelin that's protecting the axon. You can think of it, for anyone listening, is like the integrity of that white matter track to help signal processing is like a weak celery stock or a really fresh celery stock, things like that. We saw this sort of nonlinear rise. It peaked in second trimester and went down to third trimester, and then back to baseline, which kind of fits with anyone who's done the snapshot approach of pre and post pregnancy, seeing no changes in that measure. But I would say that I feel very confident that this is a finding we're going to see. I think there's a lot of signal, because your hormones, which can act as neuromodulators, are rising by 100 to 1,000 fold. In your body, which is the highest it's ever gonna be. And they've really, I think, is hormonally mediated neuroplasticity. So very confident that these changes hold up.

And as you said, I guess in some ways this is revelatory, what you found, but not surprising at the same time.

Yes, exactly. And it was really fun to sit with that data and be playing with it and trying to break And I took it to all these different labs, including someone at the National Institute of Health. And I was like, what? This is just so beautiful. Like it has to, it can't be this linear. It can't this like fitting within this literature because it's like that science is so messy. It just was fun to see kind of because you're sitting on data that no one has, at least to our knowledge, published on yet of 26 time points during that perinatal period of a person.

It's a pretty laborious study, I mean, you know, congrats to the study subjects, right? If you do become pregnant in your life based on your own research, would you do anything differently? Is there a message in there for women who might be listening who are thinking about pregnancy?

I, yes, I think that I've been asked this a few times and I've thought about it a little bit more. And I think for me, it's, I would feel so much calmer and I do feel calmer going into that life stage, knowing that certain things are normal. And I, I, think of it as like a reference range. That's what I'm trying to build actually right now is if you go get a blood test and you have say like elevated iron, but it's within like the normal range, it doesn't get flagged. That's, what I want to do for brain changes during pregnancy because that can calm me into saying: I know the literature. I know that I'm going to have maybe these memory or attention subjective feelings of that changing. OK, that's fine. Here, I'm just talk to my physician. I'm gonna talk to partner and say, if you're seeing that it's impacting my quality of life and I had more severe version of that, maybe I'll do my own sort of cognitive exams on myself. Why stop? Then I would ask, I would want to talk to a doctor about that. You know, try to seek maybe help there, but knowing what's normal or what to expect and just having more knowledge of what this is gonna be is really helpful to me. Additionally, knowing how vulnerable that first four weeks are in the postpartum, because I've seen hormones, I've see how they drop very steeply in that period and along with this, knowing that this is like one of the most heightened times in a woman's life for mood disorders and it's very prevalent. That I can go into that period knowing I need as much support as possible and here's who I'm gonna ask or I'm going to ask my partner to make sure that they're monitoring myself because you take your baby in and it has all these pediatric visits and you don't have these sort of mental health checks for the moms. You don't as much care for the postpartum mom as I think we should in our healthcare system. I think women should definitely be aware of that and talk to their partner and the people around them to help them. On the science side, we can try to make those reference frames and make the guidelines and try to improve the prediction and the treatment options for pregnant women of who's going to go on to have the most severe decompensation.

You know, I hadn't thought about that last part, starting to be predictive. On one hand, I do find it, like just trying to understand all this, we think that it would be reassuring for people. I think understanding that there are changes that happen in the brain, it's something that is common, it's related to pregnancy in this case that you're talking about. I think that's in some ways reassuring for folks. Thank you for sharing all that with us.

Yeah, absolutely, thank you for having me.

That was Dr. Laura Pritschet, postdoctoral fellow at the University of Pennsylvania, studying the effects of pregnancy in the brain. Chasing Life is a production of CNN Audio. Our podcast is produced by Eryn Mathewson, Jennifer Lai, Grace Walker, Lori Galarreta, Jesse Remedios, Sofia Sanchez, and Kyra Dahring. Andrea Kane is our medical writer. Our senior producer is Dan Bloom. Amanda Sealey is our showrunner. Dan Dzula is our technical director and the executive producer of CNN Audio is Steve Licktieg. With support from Jamus Andrest, Jon Dianora, Haley Thomas, Alex Manassari, Robert Mathers, Lenni Steinhardt, Nichole Pesaru, and Lisa Namerow. Special thanks to Ben Tinker and Nadia Kounang of CNN Health and Katie Hinman.