HomeScienceGeneticsWhat is the effect of pregnancy on resting brain activity?

What is the effect of pregnancy on resting brain activity?

During pregnancy, women undergo several changes in their bodies and behavior. A recent Nature communication study evaluated pre-pregnancy and post-pregnancy brain scans to better understand the changes in gray matter architecture, the diffusion metrics of neural metabolites, and the temporal coherence of neural networks. In addition, the biological factors associated with these changes were assessed in this study.

Study: Mapping the effects of pregnancy on resting brain activity, white matter microstructure, concentrations of neural metabolites and gray matter architecture. Image credit: Jezper/Shutterstock

Background

Pregnant women go through a monumental transition related to a cascade of endocrine and various adaptive changes in the body. Almost all body systems change during pregnancy, and some physiological changes remain consistent for decades after delivery. Limited evidence has been documented about the changes in the human brain during pregnancy and beyond.

Several non-human animal models have shown a link between reproduction and brain plasticity. These studies have shown striking changes in mammalian brains and behavior.

According to a recent study, pregnant women change the gray matter structure of the human brain. The present study went a step further to analyze the changes in pregnant women’s neural metabolite concentrations, neural network organization and white matter microstructure using an expanded prospective study cohort.

About the study

In this study, four longitudinal experimental sessions were included and participants were followed from preconception to the late postpartum period. Analytical tools, such as diffusion-weighted imaging, anatomical magnetic resonance imaging (MRI), resting-state functional MRI acquisitions, and 1H nuclear magnetic resonance spectroscopy, were used to investigate the effect of pregnancy on the human brain.

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Changes in hormonal profiles were assessed to analyze the mechanism behind pregnancy-related neuroplasticity. Maternal hormone levels were determined using biological samples collected every four weeks of pregnancy. The sleep pattern and stress level of the participants were also recorded.

The changes in the brain scans over the study period were plotted on a graph. A specific structural and functional brain plasticity was observed that could contribute to maternal adaptability during pregnancy.

Findings

Compared to non-pregnant women, a clear gray matter architecture was found in pregnant women. In pregnant women, a decrease in gray matter volume was observed, affecting the anterior and posterior cortical midline and specific areas of the bilateral lateral prefrontal and temporal cortex.

Magnetic resonance spectroscopy, diffusion-weighted imaging, and resting-state functional MRI data revealed no significant difference in diffusion metrics or white matter volume between the pregnant and nulliparous (control) groups. This finding indicates that the anatomy of a woman’s white matter remains stable during pregnancy.

The fluctuations in sex steroid hormones were selectively strong for certain brain components, i.e. the steroid hormones influence the gray matter of the brain significantly more than the structure of the white matter. Magnetic resonance spectroscopy data revealed no change in neural metabolite concentrations during pregnancy.

The Default Mode Network (DMN) corresponds to a group of highly coherently activated brains that remain highly active even without a specific task. Therefore, DMN reflects the basic activity of an individual brain. It is also heavily involved in higher-order social processes such as social evaluation, social cognition, and empathy.

MRI data on women’s resting state deciphered the neural network organization of pregnant women. This analysis revealed a selective increase in DMN in pregnant women who sat between sessions, compared to the control group. Although structural brain changes were more prominent in the DMN, the fronto-parietal brain regions associated with higher-order cognitive tasks (e.g., cognitive functions) were also affected.

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It is important for new mothers to focus on their baby’s needs and feelings and understand their emotions. Accordingly, several studies have indicated a functional change in the DMN. In addition, resting-state functional connectivity in mothers was linked to maternal behavior.

The current study speculated that structural and functional pregnancy-related alterations in the DMN alter an individual’s neuronal structure, which prepares women for motherhood. Interestingly, the neural changes in the DMN were observed to be related to the degree of bonding between mother and child.

Some of the factors that drive pregnancy-related brain plasticity are pregnancy hormones. For example, estradiol levels, especially in the third trimester, have been associated with changes in brain structure. Sleep, osmotic effects, breastfeeding, stress or the type of childbirth were not linked to structural or functional changes in the brain during pregnancy. The unparalleled exposure to estrogen during late pregnancy was found to influence pregnancy-related structural neuroplasticity.

Conclusions

Analytical data on pregnant women indicated structural and functional plasticity within the DMN, suggesting that mothers experience changes in the basic state of the brain. Functional changes in the DMN were associated with the child-directed processes, while brain structural changes were associated with simulations of preparatory behavior. In the future, a wider range of possible regulatory factors (e.g. diet, genetic markers, environmental changes and exercise) should be evaluated to better understand their role in influencing brain processes during pregnancy.

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