Summary: Researchers have investigated the neurobiological changes that occur during pregnancy and the postpartum period, clarifying how the maternal brain adapts and how these adaptations relate to maternal behavior. Fluctuating hormones—particularly estrogens—appear to drive brain plasticity across pregnancy and after childbirth.
This review builds on findings first reported in 2017 showing that pregnancy produces measurable changes in a mother’s brain structure. Still, the complex interplay between hormones, brain remodeling, and the emergence of maternal behaviors remains only partly understood and requires further study.
Key facts:
- Pregnancy is associated with measurable changes in maternal brain morphology, notably reductions in gray matter volume in regions linked to social cognition; these changes can persist for at least two years after birth.
- Estrogens are prime candidates for driving many of the pregnancy-related brain changes documented so far.
- The emotional and cognitive processes that shape the evolving mother–child relationship across pregnancy and the postpartum period remain poorly understood and represent a key distinction between human maternal adaptation and that of other species.
Source: UAB
Researchers from the Universitat Autònoma de Barcelona (UAB), the Gregorio Marañón Health Research Institute and the Hospital del Mar Research Institute have published the first comprehensive review of the neurobiological adaptations that take place during pregnancy and the postpartum period in humans and other animals.
The review, with Camila Servin-Barthet and Magdalena Martínez as first authors and Òscar Vilarroya and Susana Carmona as senior authors, appears in Nature Reviews Neuroscience and is featured on the journal’s October cover.
The authors examined 174 studies to map connections among three central domains: structural brain changes, hormonal dynamics, and maternal behavior. Their goal was to highlight evidence-based pathways for future research and to strengthen women-centered neuroscience.
Across the literature, converging evidence points to hormonal fluctuations—most notably changes in estrogens—as triggers for neuroplastic processes during pregnancy and postpartum. However, the specific cellular and circuit-level mechanisms underlying these structural and functional changes, and how they translate into maternal behavior in humans, still need clarification.
Motherhood and morphological changes
Becoming a mother is both a physiological and psychological transformation that requires multiple adaptations in behavior to care for and protect offspring. In 2017, researchers from UAB and the Hospital del Mar Research Institute provided the first evidence that first-time pregnancy alters brain morphology. They reported reductions in gray matter volume in regions implicated in social cognition, with these changes enduring for at least two years postpartum.
Subsequent studies have confirmed that gray matter volume fluctuates through different stages of pregnancy and postpartum, typically accompanied by significant hormonal shifts. The new review synthesizes these findings and identifies three key factors needed to understand human maternal adaptation:
First, estrogens (particularly estradiol) are highlighted as the primary hormonal drivers likely responsible for inducing structural changes in the maternal brain. Second, the neural circuitry involved in social cognition—including areas such as the medial frontal cortex and precuneus—is the main locus of these changes. Third, psychological shifts—encompassing the cognitive and emotional processes that form and refine the mother–child bond across pregnancy and postpartum—are crucial, and represent an area where human adaptation differs substantially from other animals.
Roadmap for future research
Based on the current evidence, the authors outline which neuroplasticity mechanisms are most likely to underlie the MRI-detected structural changes and how these processes may be linked to hormonal fluctuations and maternal behavior. They propose a research roadmap that prioritizes several avenues to advance understanding of the transition to motherhood in humans.
One primary line of research should identify the specific brain-cell substrates responsible for observed morphological shifts. Large-scale gray matter changes seen with MRI are unlikely to result exclusively from a single form of plasticity. Animal studies—particularly in rats—show that late pregnancy hormonal shifts alter neuron and microglia plasticity, with notable increases in microglial proliferation. Translating these findings to humans requires targeted cellular and molecular investigations.
A second priority is delineating how sex hormones, especially estrogens, mechanistically drive structural and behavioral reorganization. Given the complex hormonal milieu of pregnancy and postpartum and the interactive behavior of steroid and peptide hormones, it is likely that structural brain changes reflect combined actions of several hormones and metabolites. Future studies should broaden hormonal profiling, placing special emphasis on oxytocin and prolactin alongside estrogens.
The third challenge is to chart the psychological trajectory that mothers undergo during pregnancy and the postpartum period and to identify the functional brain changes that support the development of caregiver behaviors. In rodents, molecular and morphological changes often coincide with the onset of maternal behaviors; in humans, however, robust links between neuroanatomical change and discrete aspects of maternal behavior are sparse and hard to replicate.
Improving MRI methodologies, refining behavioral assessments and questionnaires, and accounting for extrinsic postpartum factors that influence caregiving circuits will strengthen our ability to connect observed brain changes with specific components of maternal behavior.
The need for more human-focused studies
Most experimental work to date has been conducted in rodents, which underlines the urgent need for more human-centered research. While there are parallels between human and animal findings, significant differences exist—particularly in cortical organization and the species-specific interplay of sexual hormones.
“There are similarities between humans and other animals, but many cerebral differences remain—especially in the cerebral cortex, the most evolved part of the brain—and hormonal dynamics differ across species,” says Camila Servin, researcher at the UAB Department of Psychiatry and Legal Medicine and the Hospital del Mar Research Institute.
“Until 2017, we had not systematically studied brain changes during pregnancy, and even now, relatively little is known about the hormonal and psychological context that shapes these changes,” adds Òscar Vilarroya. He highlights that the transition to motherhood—one of the most universal and consequential human experiences—has rarely been central in neuroscience research.
About this neuroscience research news
Author: Camila Servin-Barthet
Source: UAB
Contact: Camila Servin-Barthet – UAB
Image: The image is credited to Neuroscience News
Original Research: Closed access. “The transition to motherhood: linking hormones, brain and behaviour” by Camila Servin-Barthet et al., Nature Reviews Neuroscience.
Abstract
The transition to motherhood: linking hormones, brain and behaviour
Interest in the neurobiology of pregnancy and motherhood has grown sharply. Converging evidence indicates that around the time of labor, first-time mothers undergo a distinct pattern of neuroanatomical changes that relate to maternal behavior.
This review summarizes human neurobiological adaptations to motherhood, emphasizing interactions between pregnancy-related steroid and peptide hormones and brain neuroplasticity.
We evaluate candidate plasticity mechanisms that could explain MRI-detected structural changes, identify hormonal systems likely to contribute to those changes, and consider how such brain mechanisms may connect to maternal behavior. The review proposes an integrative framework intended to guide and prioritize future investigations into the human transition to motherhood.