The neurobiology of pregnancy and motherhood

Becoming a parent is a brain-altering experience. In this episode, Lynsey and Chrissy dive into the latest neuroscience research about what happens to the brain during pregnancy and the postnatal period. It’s pretty amazing!

If you would like to find out more about this topic, you can check out the Hoekzema lab website and read this open-access paper. 

If you or someone you know is struggling with mental health difficulties, there is lots of help available. You can contact your primary care provider in the first instance, or if you are based in the UK the NHS perinatal mental health website will help you to find support in your local area.

Transcript

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 Hello and welcome. This is Beyond Baby Blues, our podcast about maternal mental health. 

I'm Dr Chrissy Jayarajah. I'm a consultant perinatal psychiatrist working in London.

And I'm Dr. Lynsey McAlpine. I'm a trainee psychiatrist also based in London. 

This podcast is for anyone with an interest in maternal mental health. If you're a parent yourself or if you work in healthcare or social care. Or even if you just have an interest in the field of women's mental health, then this podcast is for you. 

In today's episode, we're going to be talking about some of the things that happened to the brain during pregnancy and the postpartum period. One of the challenges with looking at the research in this field is that there is a lot of neuroscience research out there. But most of the research treats the cis-gendered male brain as the normal or the default. And anything else is just seen as an anomaly or a deviation from the normal.  

So I took the more than 50,000 brain imaging studies that have been published since the nineties, less than half a percent considered health factors that are specifically related to women. 

So most of the research doesn't really take into consideration the different physiological and hormonal profiles  of women  and what that might mean for their neuro development.  

I know, it's actually unbelievable.  And it's not just about the representation, is it, Lynsey? About 50 percent of people enrolled in neuroimaging studies are women. But it's just that the female specific issues are not prioritized. 

And I suppose that's not massively surprising. Is it. Um, there's some statistics that suggest that more than 80% of tenured neuroscience professors in the U S at least are men. And that's probably shaping the direction of research. 

Absolutely., we definitely need more women, working in neuroscience for sure 

However, there are a few incredible research groups that have focused their research on the female brain, and we're going to be looking at their work today.

 Our main reference is a review paper by Dr. Hokezema and colleagues published in 2018. 

That's right. Dr. Hokezema's research group is based in Amsterdam. And they're doing some really fantastic research on the neurobiology of the female brain. It's an open access paper. So we will put the link in the episode description for anyone who wants to read it. 

So we're using a lot of terms, Chrissy. I think we should probably explain before we go any further. When we use words like neuro-plasticity, or we describe the brain as being plastic. What do we actually mean by that?  

Yeah, in this context, the word plastic refers to the brain's ability to adapt and change in response to new experiences.  In my mind, I sometimes think of the word elastic rather than plastic because it kind of bends and it can morph depending on the situation.  It does this by constantly reorganizing all of the brain's connections. 

Yeah. So basically the brain is responding to the environment and rewiring itself in response to what's going on around it. It's pretty amazing. We know that there are times when the brain has increased plasticity. For example,  during  adolescence, when the body is going through lots of hormonal changes, there's a huge amount of growth and adaption and change in the adolescent brain.  

There were two types of research that we're going to be talking about today. The first type of research looks at the structure of the brain.

This is where researchers use brain scans, usually MRI scans to the, the overall shape and structure of the gray matter and white matter within the brain.   

The other type of study we're looking at is functional MRI scans or fMRI scans. These are a type of scan that looks at the patterns of the blood flow in the brain to map out levels of activity in different parts of the brain. This tells us about the function of very specific brain regions.  

So we're looking at structure and function. If we start with the structural stuff,  chrissy, what does the research tell us about structural changes in the brain, in the perinatal period?  

So during the pregnancy, the brain volume, surprisingly, actually decreases.  We're not quite sure what causes this change, but  the study suggests that it's probably driven by hormone changes during pregnancy. We know that sex hormones have a powerful effect on brain growth.  And it's theorized that pregnancy specific hormones such as prolactin and oxytocin, which is an essential hormone for bonding, play a really important role. 

Yeah, so that volume reduction seems to mostly affect the gray matter of the brain. That appears to be a priming effect whereby the brain is preparing itself for the challenges and demands of parenthood.

And although there's a decrease in volume during pregnancy, the research indicates that in the postpartum period, the volume of gray matter starts to increase and it continues to increase for some time after the baby's born. That original 2018 paper that we were looking at showed that these changes were maintained after two years. And actually a more recent follow-up study demonstrated  that these changes are actually sustained at six years postnatal. So these are really long lasting structural changes in the brain. The go on well into the child's early life 

and in one study the researchers could tell whether somebody was a parent just by looking at their brain scans. Isn't that awesome? 

 I think what's really amazing as well is that it's not just the fact that the brain shrinks and grows in size we also know that  the maternal brain is very responsive to different environments. For example, there's a study looking at babies who were born prematurely, and it shows  that there is greater activity in the brain of these mothers showing that they're more sensitive to the baby's needs.

That's really incredible.  And another thing that I find really interesting about this part of the research was one study in particular, where they find that there's an association between these brain changes that we described and having a positive perception of their baby. And then another study where the brain changes that occurred in pregnancy predicted the quality of the mother infant attachment and the absence of any hostility towards the baby. So we can see that these brain changes are really important for priming the brain for caregiving. 

 So just to summarize these structural studies. Sure that some specific parts of the brain shrink during pregnancy. We think that that's probably triggered by hormonal cues and it's probably a priming process to help prepare the brain for the arrival of the new baby. And then we find that those same regions of the brain  expand in volume postnatally. And that's an ongoing process that's triggered and maintained by interactions with the baby. 

So that's the structural studies. If we move on now to the other type of research, the studies that look at the function of the brain. Most of these studies involve putting a mother in a functional MRI scanner and then recording the maternal brain's response to video and audio recordings of their baby or another child. That's not related to them.  These studies are great because they show that the maternal brain responses are unique and specific to her own child. And not just to any other baby that she happens to come across.  

And what these studies demonstrate is that when a mother is exposed to stimuli of her own child. there are some very specific networks within the brain that light up and become particularly active.

There are several brain networks that have been studied and we'll try and explain, a few of them. One is the maternal reward system. So this is a very powerful activation of the reward system mediated by dopamine and oxytocin,  two really important chemicals in the brain associated with love and bonding.  

That's right. And actually I saw one animal study where it found that the impact of these dopamine and oxytocin neural pathways were much more rewarding than cocaine in the animals that they studied. That's how strong it is.

Yeah. And, and it has to be that powerful, doesn't it? Because if you think about those early days of having a baby, when you are sleep deprived and they're crying and all, all the rest of it, there has to be something about this experience that makes it rewarding to keep carrying on day after day.  

Another network that's really important is the salience network. So  I describe this as sort of the mama bear network. It's how mothers have this innate sense of increased vigilance and threat detection, the example I always give when I'm working in clinic is that, you know, if you make a lovely hot cup of coffee As a parent, you would never put that cup of coffee at the corner of the coffee table on the off chance that it might spill and hot coffee goes all over your baby.

So we have this innate ability to perceive threats even before it's happened. And also to put safety and protective mechanisms in place for our children. 

Another brain network that's been studied in the postnatal period is the emotional regulation network. 

So what this does is  it allows parents to regulate their own emotional state in front of threats or while caring for their child, since we know that infants can't regulate their own emotional state very well. 

Yeah. And the reason that this is so important is that children often arouse many emotions since they express their own emotions. Very, very intensely and without much control. And in order to help the infant to integrate their own emotional experiences the mother needs to be able to effectively regulate her own emotional response to the infant if the mother becomes very distressed and dysregulated, this can be a really disorienting and upsetting experience for the infant.

The other neural networks that have been studied in great detail in parenthood are the empathy and the theory of mind networks. And these networks sort of integrate all of those other networks that we've already mentioned. So the maternal reward system, salients and emotional regulation all get brought together. 

And the totality of these networks,  allow a mother to mentalise her child. So to create a picture in her own mind of the child's mental state, as separate to her own.  So essentially what's happening here is that the maternal brain is becoming incredibly specialized in a very complex and nuanced type of social cognition. That lets the mother appraise and understand the mental state and the developmental needs of her child.

And what is really incredible about this is how these regions continue to change over the postpartum period. So where studies have looked at serial F MRI scans over time. This has demonstrated that actually these systems become more complex and more specialized as the infant grows. 

And I really love this idea that while the infant's brain is growing and developing in parallel, the mother's brain is growing and becoming much more specialized in response to her infant's brains development, which is just amazing. 

Absolutely, I think the neuroscience is so beautiful around this and, um, it's a really exciting area of  research,  and  I think it's fantastic.

Definitely.  But I suppose one of the questions that comes to mind when, when we read all of these studies, Chrissy is what about fathers and co-parents and adoptive parents. What happens to their brains in a parenting situation? 

You're right Lynsey, it's a really important question. While pregnancy and the associated brain changes can prepare a female for motherhood, it's really important to realize that this is not a requirement for mothering. There was a study in rats looking at virgin rats and how they were able to take on a caregiving role for babies belonging to other rats, what they call alloparenting.

Yeah. There's not been a huge amount of research in this area, but I did see one study from about 10 years ago that looked at the brains of human foster parents. Which demonstrated that foster parents can have brain changes in a similar pattern into what we see in biological mothers, in the postpartum period.  

So proving that actually, you know, you don't have to have a biological genetic relationship to that infant to have the same caregiving changes and effects in the brain.

And I suppose what I'm taking from that is that the pregnancy related changes that we described are amazing because they prime the brain for parenthood, but they're not essential. And a lot of the postpartum changes tend to happen in whoever is the primary caregiver. Regardless of their relation to the child.   

Absolutely. So  I guess poses another question, Lynsey, doesn't it? What does this mean for maternal mental health? We know that the brain is neuroplastic. It's shrinking and growing and responding to the environmental cues.  What we also know is that with all these changes, it's a period of greater vulnerability for development of mental disorders. 

That's right. And just to be clear, perinatal mental disorders are multifactorial. So there are lots of different biological and psychological and social factors that contribute. But given that there's such a high rate of psychiatric disorders in the perinatal period, one of the working theories here is that this increased neuroplasticity may confer an increased vulnerability to mental disorders. 

The brain is just undergoing so much change and so much development that is vulnerable to being destabilized.  And I think a lot of this neuroscientific research helps us to understand at least some of the biological mechanisms that are underlying these mental disorders.  There's very little neuroscience research about what actually happens in the brain when mothers developed perinatal psychiatric disorders. There's some emerging evidence from animal models and from  small neuroimaging studies in humans, and these are starting to detect some abnormalities in the structure, the function and the connectivity. And brain regions are specifically responsible for theory of mind, for self-regulation and for emotion regulation in mothers who developed perinatal mental disorders. However a lot more research is needed before we can draw any definite conclusions. 

  I just wanted to add, Lynsey, as well, that You know, this research has been really pivotal and it's changing the direction that perinatal mental health research is going. This paper describes how pregnancy in the postpartum period is really important and actually we should be giving mental health the recognition it deserves during antenatal and postnatal care.

 I think this episode has been really great and shedding some light on the neuroscience research that's going on at the moment. And our understanding that the perinatal brain has the capacity to change and to develop. Um, and hopefully more research to come will help us understand what is actually going on in the maternal brain.

That's right. And if we could understand better on a neuro-biological level what's happening when people develop mental disorders in the perinatal period. Then that could help us to target and improve our clinical care. So for example, we might see for the research in this field that might help us to understand why some people are at particularly high risk of becoming unwell in the perinatal period.

And it might help us to predict who's at risk so that we can target preventative treatment. 

It will also help us to have an earlier and more accurate diagnosis of  perinatal mental health conditions. And by doing that, we will be able to better develop treatments for perinatal disorders. 

For sure. So hopefully we'll see a lot more research in this area, in the future.  

Well, that's all we've got for today's episode, but if you are interested in this topic, there are some really fantastic resources out there. So do check out the episode description for links to the resources and references for this episode. 

Absolutely and We are literally just scratching the surface on the science around perinatal mental health. So stay tuned. There's lots of stuff coming in the podcast. 

Yeah, definitely. I'm looking forward to it. 

So as always a huge thank you to the Royal college of psychiatrists and specifically to the perinatal faculty for their support with this podcast. And if you'd like to hear more about maternal mental health, you can subscribe and find all of our podcasts on Spotify, apple podcasts, or wherever you get your podcasts.