More than 140 million women give birth each year worldwide and there is no doubt that pregnancy is probably the most transformative time in a woman's life. It is indeed well known that pregnancy has a considerable impact on the physical and mental health of a pregnant woman. But to what extent does it affect the brain? By analyzing the brains of pregnant women for the first time using neuroimaging techniques, a study has revealed the dynamic evolution of this organ during pregnancy and the postpartum period… And clearly, the changes are considerable , particularly at the level of gray matter.
First of all, a reminder: what is gray matter?
Gray matter and white matter are all two essential components of the central nervous system. About 40% of the brain is made up of gray matter while 60% is made up of white matter. Gray matter is mainly made up of the cell bodies of neurons which play a role key role in information processing and regulation of various cognitive and motor functions.
Located in the cerebral cortex as well as in certain deep structures of the brain such as the hippocampus and the basal ganglia, it is involved in fundamental processes such as memory, decision making, movement control and sensory perception. Unlike white matter which ensures the transmission of signals between different regions of the brain, gray matter is the headquarters for information analysis and integration. It is therefore essential to understand how pregnancy can alter this structure and what the short and long term implications are.
This is precisely what the researchers sought to elucidate by analyzing the structural changes in the brains of pregnant women over the months using advanced neuroimaging techniques.
Revealing structural changes in the brain during pregnancy
Researchers from the Autonomous University of Barcelona (UAB), the Gregorio Marañón Health Research Institute and the Hospital del Mar Research Institute, in collaboration with other prestigious international institutions have published the first longitudinal study in neuroimaging (magnetic resonance imaging) on a cohort of 179 pregnant women to monitor structural changes during the second and third trimesters as well as the first six months postpartum. Scans taken before conception also provide reference data.
This study is the first to confirm the increasingly widespread hypothesis that gray matter volume follows a U-shaped evolution throughout pregnancy. « We reveal a U-shaped trajectory of gray matter volume which decreases at the end of pregnancy and partially recovers postpartum », summarize the authors in their research.
Above all, this research published in Nature Communications shows that these changes affect 94% of the brain and are particularly visible in the default mode network (DMN), a region associated with social cognition. “ The volume of gray matter decreases during the second trimester (by 2.7%) and just before delivery (by 4.9%). These changes are symmetrical in both hemispheres of the brain, with the most marked decreases in regions of the MPD and frontoparietal cortex. », specifies the study which also indicates that the gray matter which decreases partially recovers after childbirth.
-A link between these changes and pregnancy hormones
In order to differentiate the biological effects of pregnancy from the experience of motherhood, the researchers included non-pregnant mothers in the study, here more precisely women whose partners were pregnant. However, the results obtained confirm that the changes observed in the brain were mainly due to the biological processes of pregnancy. “ Hormonal assessments suggest that these changes are caused by estrogen fluctuations associated with pregnancywith estriol sulfate and estrone sulfate identified as key factors, rather than experience of parenthood », Indicates the study.
As a reminder, estrogens are indeed hormones essential for sexual development and reproduction in women. Their rate increases during pregnancy before returning to a baseline level after childbirth. This research thus demonstrated that greater fluctuations in estrogen levels were correlated with more significant decreases in gray matter volume during pregnancyfollowed by a more marked recovery postpartum.
More importantly, by analyzing the possible influence of brain changes on maternal behavior, the study found that women who had a higher rate of recovery of gray matter volume after childbirth reported a stronger bond with their baby at six months postpartum. Maternal well-being thus appears to be a key factor that favors the association between brain changes and the mother-child bond.
Why is this important? A crucial advance in maternal brain research
In summary, these results provide new insight into how pregnancy reshapes the brain while highlighting the role of hormonal changes in the reduction of gray matter volume, all modifications which seem to prepare the brain for the demands of motherhood with potential long-term effects on cognitive and social functions.
The data obtained thus not only constitute an essential reference for understanding the neurobiology of the maternal brain, but they also serve as a basis for future studies to explore other neuroimaging modalities and more diverse samples which would notably include women who present clinical disorders such as postpartum depression. This could then make it possible to progress towards an understanding more complete and applied to the brain during this essential period of lifebut also towards better support for the health and well-being of those primarily concerned.
You can view the full study at this link.
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