Being a mother transforms women physiologically and psychologically and entails a series of behavioral adaptations aimed at ensuring the well-being of their children. Spanish scientists from the Autonomous University of Barcelona (UAB), the Gregorio Marañón Health Research Institute and the Hospital de Mar Research Institute have carried out a study in which they have reviewed the available scientific literature on the neurobiological adaptation to motherhood, analyzing the relationship between hormones, brain and behavior during pregnancy and the postpartum, and have reached conclusions that will serve as a basis for new research.
The results have been published in Nature Reviews Neuroscience and support the hypothesis that hormonal fluctuations, especially estrogen, are related to changes in human brain structure, although it is still necessary to determine how they influence neuroplasticity and maternal behavior. .
Researchers from the UAB and the Hospital de Mar Research Institute were the first to demonstrate, in 2017, that pregnancy involved changes in the brain morphology of first-time mothers, which consisted of a reduction in the volume of gray matter in areas involved. in social relationships, and that these changes were maintained for at least two years after childbirth. In recent years it has been observed that the volume of the gray matter of the brain varies in the different stages of motherhood and postpartum, and that this is accompanied by extreme hormonal fluctuations.
Morphological changes in the brain associated with motherhood
Researchers describe for the first time three key factors for understanding adaptations to motherhood in humans. The first, estrogens (estradiol) as the main candidate hormones to induce brain changes. The second, the brain circuit related to social cognition (with the medial frontal cortex and the precuneus, among other areas) as the region where these changes especially occur. And the third, psychological changes, that is, the cognitive and emotional processes necessary to develop an adaptive mother-child bond in the various phases of pregnancy and postpartum. This third factor is the one that differs the most from other animals and is barely known.
All evidence suggests that hormonal fluctuations are what trigger brain plasticity processes during pregnancy and the postpartum period.
The researchers have reviewed 174 articles in which they have analyzed the connections in three fundamental areas such as brain changes, hormonal evolution and maternal behavior, with the aim of establishing new lines of study to advance research in women. All the evidence, as the researchers detail in their article, suggests that hormonal fluctuations, mainly related to estrogen, are what trigger brain plasticity processes during human pregnancy and the postpartum period.
However, more studies are needed to determine what types of plasticity processes – involving changes in cellular function, brain structure and connectivity – are involved in the transition to motherhood in humans and how they affect maternal behavior. .
Based on published evidence, researchers have pointed out which neuroplasticity processes are most likely to contribute to the identified changes, and how they may be related to pregnancy hormones and maternal behavior. They have also drawn up a roadmap with several lines of research to advance the study of adaptation to human motherhood.
A first line of research would be aimed at identifying brain cellular substrates. The large-scale dynamics of changes in gray matter are unlikely to be produced exclusively by plasticity at the morphological and molecular level, experts say. In rats, it has been seen that the fluctuation of hormones, especially in the last stage of pregnancy, affects plasticity in neurons and microglia, with greater proliferation of this second cell type.
Another branch of research would include the description of the mechanisms that explain how sex hormones, especially estrogens, induce the changes in structural and behavioral reorganization detected. Given the hormonal environment that occurs during pregnancy and the postpartum period and the interactive nature of these molecules, the changes are most likely caused by a complex exchange between multiple steroids and hormonal peptides. To better understand its role, a greater number of hormones and metabolites should be studied, with special attention to oxytocin and prolactin.
Finally, it would be necessary to identify the psychological evolution during pregnancy and the postpartum period and characterize the functional brain changes responsible for the development of human behavior. In studies with rats, molecular and morphological changes that accompany the emergence of maternal behavior have been observed. In humans, the association between neuroanatomical changes and different aspects of maternal behavior are also few and difficult to replicate. Improving the methodology in studies with magnetic resonance imaging in humans and in questionnaires would allow us to better infer the link between the observed brain changes and different components of maternal behavior. Extrinsic postpartum factors should also be taken into account, which could induce changes in the circuits related to maternal care.
Source: Autonomous University of Barcelona (UAB)
