"One pregnancy is stupid for three years"? No, it's a brain revolution during pregnancy

intelligentsia

2024-05-13 16:10Published on the official account of Jiangsu Science New Media Intellectuals

Source: Pixabay

Written by Zhang Ping

Editor-in-charge | Li Shanshan

In an obstetric textbook circulating in Europe in 1848, it was written: "Her (woman's) head was too small to express intelligence, but it was large enough to accommodate love." ”[1]

It is also enough to accommodate maternal love.

More than a hundred years have passed, and the narrative of the intelligence of the woman who became a mother has not only not changed, but has become more and more entrenched, and even the mother herself is convinced. Whether it's the Chinese proverb that says "one pregnancy is stupid for three years" or the "Mommy Brain" in Western society, the ubiquitous and inevitable mainstream stereotypes still control women's attitudes towards women, and even a large number of researchers view mothers. There is no doubt that we should certainly take seriously and understand the forgetfulness, slow reaction, and lack of concentration of mothers, and we should be aware of the distress cries hidden behind the "pregnant stupid" complaints. But, can you change the word? Can you not be "stupid"?

Our long-held belief that the "mom brain" doesn't give a complete picture of how a woman's brain works during the process of becoming a mother and throughout the life stages thereafter. In fact, mom's brain is not "stupid"! It is thought that memory deficits, the brain is no longer functioning properly, is a normal trait of being a mother, but this is not scientifically true. So, how does having a baby change the brains of women (and caregivers of all genders)? How does it affect mothers?

Pregnancy is similar to "puberty"?

Without exception, everyone goes through such a process at some point in their lives: emotional and moody; Pustules and pimples gush out of cracks in the skin; Your body grows in strange places and grows very fast.

As a mother, you will quickly think of the stage of your pregnancy, and those who have never experienced pregnancy will think of your own adolescence first. But have we ever wondered if there is a subtle or strong commonality between the two? The same goes through a drastic change in hormone levels, the same extreme physical changes, the same into a whole new self, a new role. But no one ever called them stupid. On the contrary, their high morale, fierce rebellion, and fearless courage are talked about, and every adult envies their youth.

If the brain changes that occur during pregnancy cannot be summed up simply as "being stupid", then we have to wonder if it is possible to become a mother, as much as adulthood, is it just a complex process of adapting to a new identity?

A group of female neuroscientists challenged this.

In 2016, a group of female neuroscientists, led by Elseline Hoekzema in the Netherlands and Erika Barba-Müller in Spain, published a landmark study in Nature Neuroscience [2]. For the first time, conclusive evidence is provided that pregnancy causes significant, consistent, and persistent changes in brain structure. Previously, little was known about the effects of pregnancy on women's brain structures.

In the study, after analyzing first-time pregnant and non-pregnant women using neuroimaging digital technology, the researchers found that pregnancy resulted in a significant reduction in gray matter volume in the cerebral cortex in both prefrontal lobes, bilateral temporal lobes, and anterior and posterior midline locations, while also observing a decrease in cortical surface area and thickness. These structural changes were strikingly consistent in pregnant women, in other words, images of changes in gray matter volume and cortical thickness in the brain could be used to accurately distinguish between pregnant and non-pregnant women. Not only that, but these changes persist for at least two years postpartum.

The research team has speculated that similar changes in the brain occur during adolescence due to the sharp increase in sex hormone levels in the body, similar changes in the cerebral cortex occur during pregnancy. To confirm this intuition, the same research team confirmed this hypothesis in the laboratory of another female neuroscientist, Susanna Carmona (who is also an artist), in Madrid [3]. The team compared the brains of 25 first-time mothers and 25 female adolescents and found that their structural changes were strikingly similar. Gray matter volume decreased at almost the same monthly rate in each group; Both groups were accompanied by changes in cortical thickness and surface area, as well as a decrease in the gyrus (the part of the cerebral cortex that is raised) index, a decrease in the depth, length, and width of the sulci (the folded part of the cerebral cortex).

"Our findings are consistent with the idea that the morphological changes in the brain associated with pregnancy and puberty reflect hormone-induced similar biological changes," the team concluded.

Gray matter is atrophy, cortex is thinning, and it sounds like the brain may be deteriorating, or losing some of its abilities. After the publication of this study in 2016, many media outlets took advantage of it to make a big article: "Pregnant stupid hammer! "One pregnancy is stupid for three years to find scientific evidence!" But they may not have read the full texts of the studies carefully, and the researchers didn't stop there.

The research team was curious about why gray matter atrophy did not occur randomly in the subjects. Does a particular area prove that they are responsible for a specific function? Digging further, they discovered some very interesting phenomena that have yet to be explained. For example, there was no difference between the brains of a first-time father and the control group. In addition, the brain regions where gray matter atrophy occurs are also the areas that are primarily responsible for social cognition, that is, the areas of the brain responsible for dealing with social interactions between people—how they perceive, how they interpret, how they react. As a mother, what do you need to be most prepared to deal with when interacting with whom? Husband? Doctor? Colleague? Or the boss? The answer is self-evident, of course, her newborn baby.

Could it be that the structural changes in the brain are a series of preparations to adapt to the challenges of becoming a mother?

Could it be an evolutionary mechanism to ensure that the fetus is properly cared for and has a higher survival rate after birth?

Could it be an evolutionary mechanism to ensure that mothers are not driven insane after birth and have a higher maternal survival rate?

Curiosity is like a rabbit hole, and once you get into it, you can have big adventures. To further investigate the possibility of restructuring the brain to accommodate motherhood, the research team used the Postpartum Attachment Scale to assess the relationship between brain changes and the mother's attachment index to the newborn. The results showed that changes in gray matter volume in pregnancy significantly predicted the quality of mother-infant attachment and maternal hostility to the neonatal after delivery, and the more drastic the cortical changes, the less hostility the mother was to the baby. In addition, when the researchers showed the mother a picture of her baby, the mother's ventral striatum — the area of the brain involved in the brain's reward system — lit up like a light bulb and overlapped considerably with the area of the brain where gray matter volume had been reduced. It turns out that "I've never smelled as wonderful as my baby's body" is a powerful biological drive that evolution is etched into our brains.

As a mother, "I love experiencing this powerful biological drive," says Dr. Hoekzema, one of the paper's first authors and now director of the Pregnancy and Brain Laboratory at the University of Amsterdam Medical Center, while the underlying cellular processes are still to be discovered, "the changes we observe throughout pregnancy are likely representative of a specialization of the female brain and help help women transition to motherhood." ”[4]

During adolescence, gray matter volume reduction is thought to be a specialization, specialization, and refinement of brain circuits, representing the elimination of weak connections between nerve cells to fine-tune the network to accommodate the range of behavioral, cognitive, social-emotional, and physical changes that occur as humans transition from childhood to adulthood [5]. For adolescents, the part of the neural circuit that was originally responsible for "boys and girls are the same" is eliminated, and in its place, "boys and girls are different" and the part of the neural circuit that creates shame about their own bodies is established. For mothers, the development from being a self-directed individual to being responsible for another life, further expanding self-awareness, also requires fine-tuning neural networks.

Adolescence and motherhood are both sensitive neuroremodeling windows that are necessary to adapt to the new demands of life. They are also one of the most dangerous and sensitive periods in the course of life, however, the process of a woman becoming a mother does not deserve a proper noun. There may be, but it has never been mentioned.

In 1973, American medical anthropologist Dana Raphael coined a new term in her fieldwork on pregnancy among women in the Solomon Islands: MATRESCENCE, the time of mother-becoming, [6]. Raphael sees this as a critical period for women who were neglected by the West at the time (and not taken seriously by Western society now), in which the woman's physical state, her place in the group, her emotional life, the focus of her daily activities, her own identity, and her relationship with everyone around her change. Rapid, extreme changes in hormones and environment during pregnancy mark a girl's transition to motherhood, a major biological/social/life event that represents a sensitive period of neurocognitive development: motherhood.

"But Mom is really stupid"

Not everyone is satisfied with the findings of this group of female scientists who are trying to overturn the stereotype of "pregnant stupidity". Especially moms. In the process of pregnancy, losing three things is real, forgetting to talk is real, being unresponsive is real, turning on your phone and not remembering what to do is real, forgetting to bring your travel documents before going out are all real. If it's not pregnancy stupidity, is it "me" lying?

Studies have shown that up to 80 percent of pregnant women report subjective experiences of cognitive decline during pregnancy [7]. Here, we need to note that cognitive decline does not mean a decline in intelligence, but rather a decline in a range of cognitive domains, including memory loss, difficulty concentrating, etc. Subjective cognitive ability refers to a questionnaire that the researcher asks the subjects to self-assess at a convenient time, and the test questions are usually simple and straightforward, such as: "Do you think you have memory loss after pregnancy?" At the same time, of course, the researchers will be cautious about subjective reports, so objective methods such as neuropsychological assessments and cognitive tasks will be used to test them according to the purpose of the experiment. These tests are usually performed face-to-face with researchers in a clinic or laboratory setting, and each test has more than a dozen or twenty pages of worksheets. Questions come in many forms, such as graphics, numbers, words, language, etc. When the researcher read a list of words and asked them to memorize them, it was as if the subjects were returning to school for a final exam.

The results of the objective test are also unquestionable, and the mothers are not moaning or clever words, nor are they pretentious or bluffing. Multiple meta-analyses have demonstrated objective cognitive decline in pregnant women in addition to self-reported memory loss during pregnancy [8–10], with persistent memory decline during pregnancy, most pronounced in the third trimester. This is consistent with the literature results in rodents (rat mothers) [11]. In humans, these declines are subtle and remain within the normal limits of general cognitive function and memory [12]. Therefore, while cognitive decline may be a significant change for pregnant women compared to pre-pregnancy baseline, they are unlikely to disrupt daily life.

Unlike subjective cognitive decline during pregnancy that matched objective measurements, there was a difference between objective tests and subjective reports among postpartum mothers. Moms consistently reported subjective memory impairment without measuring a statistically significant decline in cognitive level [13]. No objective evidence of maternal cognitive decline was found after a breakdown of cognitive function in all relevant studies, and these studies consistently showed that postpartum mothers reported memory loss in the absence of objective cognitive differences [14].

In addition, a number of studies have found that both rat mothers and human mothers appear to have a trajectory of cognitive normalization again, which means that the cognitive decline that occurred in the third trimester and early postpartum period gradually recovers, and even some cognitive improvement occurs at weaning (in rodent studies, rat mothers have been shown to have better cognitive level tests, such as memory and social learning ability, after weaning than before pregnancy [15]). A small number of studies on human mothers show a similar cognitive trajectory. [16] Overall, pregnancy does cause some cognitive decline in mothers, but these declines disappear after giving birth, and mothers may even become "smarter" after weaning and later postpartum.

We can't help but wonder why objective memory tests don't match what moms actually experience or feel.

In 2023, three female neurologists and psychologists jointly published an article at JAMA, in which they proposed to reshape the image of the "mom brain" and conceptualize the transition to motherhood as a new "developmental period" we mentioned above—the motherhood period, so as to prompt us to take a broader and more holistic view of the mother's brain during this critical period, and consider the importance of these adaptive changes in brain function. At the same time, they hypothesized that objective tests contradict subjective feelings: ecologically relevant stimuli and attributional biases. [17]

As a very simple example to explain ecologically related stimuli, it is impossible to expect rats to react to the perfume of the researcher rather than the scent of a snake to secrete stress hormones, because the former is not ecologically relevant to rats in the natural environment. Therefore, they believe that if we re-examine and understand the mother's memory through the lens of "redevelopment", we will find that the mother's memory is not memory loss, but memory enhancement. We already know that after becoming a mother, the brain adjusts its structure to adapt to new roles. So it's easy to understand that being a parent, where to put the travel documents you used two months ago, the names of the clients you met last week, the tasks assigned by your boss yesterday are no longer ecologically relevant for mothers. As a new mother, the cognitive load is more challenging than any stage of life, and the brain adjusts circuits to free up resources to memorize baby-related items, aka ecologically relevant stimuli.

No mother would object to her amazing accuracy in memorizing where her baby's belongings are placed, the number of times her baby urinates and feeds in a day, and the birthday and preferences of her child's school math teacher. Consistent with our intuition, the researchers also found that pregnant women had an enhanced ability to learn and remember baby-related items, while also having better long-term memory than women who had never been pregnant [18]. In another study by the same team, the same team noted that pregnant women in the third trimester of pregnancy showed a general increase in hippocampus-dependent spatial associative memory and a specific enhancement of memory in response to infant-related stimuli compared with nonparous controls [19]. Spatial associative memory is our ability to learn and remember spatial locations, for example, the placement of diapers, feeding bottles, and breast pumps at home. Memorizing the spatial location of objects needed for survival is a basic adaptive behavior necessary for humans and animals, and it seems that the mother's brain is firmly controlled by her child. In fact, there is every reason to think that moms' memory is not declining, but actively reorganizing, fine-tuning, and readapting.

Daniel Kahneman, the father of behavioral economics, tells us in "Thinking, Fast and Slow" that the brain's unconscious, fast, and less brain-intensive "System 1" dominates our thinking patterns, and it also brings with it many cognitive biases. Decades of psychological research have shown that attribution bias is very common in our daily lives, for example, if you are driving on the road and another driver suddenly overtakes you and grabs you, our normal first reaction is to blame the driver of the other car for being reckless rather than thinking of other situations that might exist. Attribution bias is one such thinking fallacy, which is the personality tendencies, personality traits, or attitudes that we habitually attribute to individuals in the process of interpreting behavior. And "mommy brain" may be a typical example. Ordinary people and even scientists are influenced by the dominant narrative of society, and tend to emphasize many small and commonplace behaviors, such as forgetting what to say and misplacing the key, as "pregnant stupidity". And the increase in cognitive load also creates more opportunities for forgetting. In addition, the mother's increased cognitive expectations of herself also make the mother more acutely aware of her slight forgetfulness or lack of concentration.

In addition, given that mood problems and sleep disturbances are common during pregnancy and the postpartum period, the association of cognitive changes with these is noteworthy [20].

All in all, the brain is "remodeled" in preparation for raising children. Without these preparations and changes, the mother maintains the brain structure and cognitive patterns that she had when she was single, and the baby will not survive without her full attention. Neuroadaptation, which allows the mother to manage new, difficult tasks and build strong attachment relationships with the child, is also a survival strategy for the fetus implanted in the mother's brain (and it is also true that fetal cells are found in the mother's brain!). [21]）。

Being "stupid" is not the whole truth of the mother's brain, it's time to give the mother's brain the honor it deserves.

Raising children, but also exercising the brain?

In 2023, a team of researchers from Yale University, led by female neurologist and psychologist Edwina R. Orchard, published a scientific review in Cell using the term "MATRESCENCE", in which they made a bold claim that motherhood has positive effects on women's brain and cognitive abilities that last a lifetime [22]. The Yale team also argues that, from a societal perspective, the role of motherhood is not limited to gender (e.g., male, female, non-binary) or gestational relationships (e.g., biological, non-biological).

As early as 2022, the team found that during the perinatal period, between 28 weeks of gestation and one week postpartum, there is significant neuroplasticity and cognitive adaptation in the mother's brain, which means that exposure to the baby makes the mother's brain "more flexible, more responsive, and more efficient" [23]. Now they go further and point out that mothers have become "smarter" as a result of pregnancy and parenting. All the experiences of the mother can be regarded as "wisdom deposits" in the brain, and these new "wisdom deposits" are long-lasting and valid for life during the mother's life stage. The higher the complexity of parenting, the larger this "saving" amount, increasing the mother's cognitive reserve in later life, and the better she can cope with future crises in case of emergency.

Every mother understands that motherhood is a job without work and holidays. Over time, when you think your baby will be better off when you start sleeping through the night, you find yourself pregnant with a second child; thought that it would be easier for the second child to "raise pigs", and he had to start preparing for the eldest to be younger; When the second child is on the right track to go to school, the eldest has reached the age of "running away from home". Motherhood seems to be a Sisyphusan curse on women's backs, and as the early challenges are slowly solved, they find that the next one is just around the corner. The cumulative effect of multiple births, or the overlap of the needs of children due to close proximity of births, exacerbates the problem. Motherhood is a constant battle, and while motherhood may build mental and physical resilience over time, and sleep and social support increase as the child grows, the complexities of the mother's environment never fully return to the level it was before the child was born. As children grow, their needs change and the mother needs to constantly make behavioral adjustments. For example, caring for a newborn who is completely dependent on an adult is completely different from caring for a young child with limited mobility, and school-age children require different care than adolescents. In this way, the complexity of the mother's environment is influenced by the child's stage of development, which constantly adapts to the environment that is always changing. In addition, because individual children exhibit different temperaments, a set of skills and strategies for getting along with the eldest does not work at all with the second, which requires the mother to relearn and dynamically evaluate parenting styles.

The bad news is that long-term exposure to the complex environment of childbearing can cause the mother to be exhausted, but the good news is that it is good for the mother's brain and may also increase the mother's cognitive reserve in later life. The positive correlation between reproductive experience and neurocognitive improvement in maternal midlife is well documented and widely accepted in rodents. Maternal rodents experience improved spatial learning and memory in middle age, decreased hippocampal amyloid deposition (amyloid deposition thought to be an early feature of Alzheimer's disease), and decreased memory in later life [24]. It is not controversial that the long-term cognitive and brain health of the rat mother benefits from its reproductive experience, and the Yale team proposed the environmental enrichment hypothesis to explain this phenomenon.

Environmental enrichment refers to the stimulation of the brain by enriching the physical and social environment. For example, older adults are often advised to delay brain aging by participating in senior colleges, social events, puzzle games, etc., which is to use the environmental enrichment effect to promote brain health. This is because the brain has a more efficient synaptic production rate and more complex dendritic growth in a richer and more stimulating environment, which enhances brain activity. This effect occurs mainly during neurodevelopmental development in children, but it can also occur to a lesser extent in adulthood. Environmental enrichment has been shown to improve cognitive function in children, reduce memory impairment, and reduce the risk of dementia in older adults [25].

Basic studies have shown that rat mothers exhibit similar cognitive and neurological outcomes as those under the influence of environmental austerity [26,27]. Mother rats with poor environment exhibited thicker cortical depth compared to rats in the laboratory in environmental enrichment, suggesting that the environmental richness associated with motherhood was sufficient to offset the adverse effects of a poor physical environment. The results of this experiment were replicated at a later stage. The average cortical depth of female mice was higher than that of virgin females in all rearing conditions. Maternal rodents have enhanced learning and memory and increased neuroplasticity compared to virgin females. A similar association exists in primate fathers who are involved in raising their offspring. Brain changes in paternal marmosets are similar to those in the abundance environment, and this effect is thought to be mediated by paternal-infant contact [28].

The Yale team believes that "this [the results of the rodent study] may be applicable to human parents". The two main factors of the enrichment environment are complexity and novelty [29], both of which increase in human parental care settings, for example, as mentioned earlier, mothers are faced with new tasks and behaviors related to their children; Parenthood adds to the complexity of everyday senses, cognitions, society, and the environment.

If the theory of environmental abundance is mainly applicable to animal models and is not sufficient to describe changes in humans, the research team has proposed another related concept, cognitive reserve [30], to speculate on the long-term benefits of parenting for human mothers. Cognitive reserve is when the brain stores pre-existing cognitive processes to defend against cognitive decline brought on by injury, disease, or aging.

For example, individuals with high cognitive reserves have a slower rate of decline in memory, executive function, and language skills during healthy aging. People who are exposed to challenging and complex environments have higher cognitive reserves, including higher levels of education, professionalism, participation in complex social activities, cognitively demanding hobbies, and learning a foreign language, all of which are associated with increased cognitive reserves in later life.

The research team believes that mothers go through quite complex environments throughout their lifespan. Drawing an analogy between motherhood and occupational complexity, if the type of work a person does in their lifetime contributes to their cognitive reserve in their later years, then we should expect motherhood that provides novelty, complexity, and a commitment not to "leave" for decades to also increase cognitive reserve. In fact, the idea that parenthood increases cognitive reserve has been circumstantially evidenced in the cognitive reserve literature [31]. The Cognitive Reserve Index Questionnaire (CRIq) is a standardized measure of an individual's accumulated cognitive reserve over their lifetime, based on their education, work activities, and leisure time. Studies have shown that individuals with more children or more frequent caregiving responsibilities (whether caring for children or the elderly) score higher on the CRIq, reflecting the impact of these activities on cognitive reserve. In this way, the cognitive load of production and parenting that challenges mothers may be beneficial in the long run, as it creates ongoing environmental complexity throughout the lifespan.

Another circumstantial evidence is that there has been a large body of research that confirms a complex relationship between parity, or the number of children born, and the brain age of middle-aged mothers and Alzheimer's disease. Analysis of MRI brain scans using machine learning to assess brain age has shown that among middle-aged mothers, mothers who have more children exhibit "younger-looking" brain structures [32]. Interestingly, more children are not always better. In a large study of cognitive testing in middle-aged women, parity was associated with cognitive performance in an inverted U-shape, with lower parity (less than two children) and higher parity (more than five children) associated with poorer cognitive performance, with the best cognitive performance observed in mothers and fathers with two to three children [33]. The association between multiple births and poorer cognition may be determined by socioeconomic status, while the association between childlessness and poorer cognition is not. Studies of dementia risk have also shown a consistent inverted U-shaped association between women and men [34], i.e., those with two children are at the lowest risk.

However, in the face of these massive amounts of preliminary studies, the research team also cautions against interpreting these results, and the reliability of the data distribution is affected by complex socio-demographic factors and the reliability of statistics themselves. In addition, the underlying factors that cause people not to have children, including the influence of genetic or other biological factors that affect fertility, must also be considered. In other words, it is difficult to explain the relationship between the number of children and cognitive performance and the risk of dementia until a richer phenotype and representative sample is collected and/or available, nor does it mean that women with less or no parenting experience have worse cognitive levels in old age.

End

So, have scientists denied the existence of "pregnant stupidity"?

Readers who have been reading academic articles for a long time may be acutely aware that there is no lack of indirect, preliminary, and basic studies in the above-mentioned studies, and the results are all correlated, which can only support the researcher's guesses, and cannot prove the conclusive causal relationship between the research variables. However, does it really take such a rigorous, flawless, and meticulous reason to change the name of "pregnant fool"? Could it be that in addition to being "stupid", those anxieties, nervousness, guilt, aggressiveness, frustration, disappointment, anger and fear are completely absent from mothers? Shouldn't mothers be affirmed for their agility, wit, intelligence, multitasking, and gentle and unwavering empathy in their parenting? Doesn't this extraordinary period that women are going through deserve a more respectful word to narrate?

Whether you have an accidental pregnancy or planning to become pregnant, whether you have been naturally or artificially inseminated, whether you have experienced several births and several children, whether the transformation of motherhood is unexpected or beyond your imagination, whether being a mother has caused you a lot of pressure or you are fortunate to have reliable social support, whether you feel that pregnancy has enriched your life or that it has made you incomplete, we cannot deny that motherhood is a woman's "natural" mission, The physiology of women is a high-level evolutionary mechanism of nature in order to preserve the species, and at the same time, we cannot get rid of motherhood, the identity that society has constructed for us.

Beauvoir once said in The Second Sex that the so-called maternal "instinct" does not exist. But now we see it, and it does exist. What if motherhood comes with a gift at the same time? What if all the hesitations, pains, struggles, happiness, fulfillment, exhaustion, busyness, moving, joy, sadness, confusion, sweetness, surprises, blood gushing, tenderness and tenderness that have become the mother's experience will become some form of accumulation of wealth in our minds and bodies over time? I am convinced that our bodies themselves have a kind of physical memory. I love the title of his classic book, Bessel van der Kolk, a well-known American trauma expert: The Body Keeps the Score. Our experiences shape/reshape our bodies, and even though it can be silly for three years to get pregnant, we also become healthier, more sensitive, more decision-making, and more resistant to aging.

If you think about it this way, can you give every woman who is struggling with family and career a little peace and relief?

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