Researchers at University College Cork, Ireland, have published a scoping review in PLOS ONE, analyzing existing studies on the effects of perinatal maternal stress on maternal and infant gut microbiota, as well as breastmilk microbiota. The review, which systematically maps available evidence, offers a deeper understanding of how maternal stress during pregnancy and the postnatal period affects both mothers and infants.
Background and Scope of the Review
The review highlights that stress during pregnancy and the postpartum period is not only a psychological challenge for many women but also a significant factor in altering the microbiota. Researchers found notable inconsistencies in stress measurement methods, with self-reported stress often not aligning with biological markers like cortisol levels. Maternal stress during this critical period can be triggered by numerous factors, including lack of social support, work and family responsibilities, and complications during pregnancy or childbirth.
The global prevalence of perinatal maternal stress varies, with estimates ranging from 5% to 93%, and evidence suggests that this stress may have worsened following the COVID-19 pandemic, although conclusive data remains limited.
Early exposure to maternal stress has been linked to higher risks of metabolic, immunologic, and neurobehavioral disorders in infants. Maternal microbiota, including gut, vaginal, and breastmilk microbiota, plays a pivotal role in infant health, influencing their immune and metabolic development. The review explores how stress-related alterations in maternal microbiota may be transferred to the infant, potentially predispositioning them to inflammatory conditions and other adverse health outcomes.
Review Methodology and Findings
The authors conducted an extensive search across multiple electronic databases, identifying seven studies that met their review criteria. Two of these studies focused on the impact of maternal stress on the gut microbiota of mothers, while five assessed the infant gut microbiota. A significant gap was noted, however, as no studies explored the direct relationship between maternal stress and breastmilk microbiota.
The review found wide variability in microbiota changes due to stress, suggesting that other factors like diet, delivery method, and antibiotic use also influence microbial composition. In five of the seven studies reviewed, higher levels of maternal stress were linked to an increased presence of potentially pathogenic bacteria, including Erwinia, Serratia, Terrisporobacter mayombei, and Bacteroides. Conversely, lower stress levels were associated with an abundance of beneficial bacteria such as Lactococcus, Lactobacillus, and Akkermansia.
However, one study presented contradictory results, showing that higher maternal stress increased the abundance of beneficial bacteria. This highlights the complexity of the relationship between maternal stress and microbiota, suggesting that different measurement methods and timing of stress exposure can lead to divergent findings.
Stress Measurement Inconsistencies
The review also underscores the limitations of relying solely on subjective self-reported stress assessments, such as the Perceived Stress Scale or Daily Hassles Scale. These tools were associated with less consistent findings regarding microbiota composition. In contrast, studies incorporating biological markers like cortisol levels and cytokine analysis showed more consistent associations between maternal stress and microbiota changes.
The authors emphasize the need for improved research designs that combine both subjective and objective stress assessments to obtain a more comprehensive understanding of how maternal stress influences microbial environments.
Implications and Future Research Directions
The findings of the review suggest that perinatal maternal stress has the potential to significantly affect the microbiota of both mothers and infants. While some studies showed that maternal stress led to an increase in pathogenic bacteria, others suggested a beneficial shift in microbial populations. This inconsistency points to the importance of considering various factors—such as the type, timing, and duration of stress exposure—when researching the impact of stress on microbiota.
To address these challenges, the review calls for more comprehensive studies that integrate psychological assessments, biomarker-based evaluations, and longitudinal sampling. Tracking microbiota changes over time will help clarify the precise mechanisms through which maternal stress influences both maternal and infant health.
Ultimately, the review highlights a pressing need for further research in this field, with the goal of better understanding the long-term health implications of perinatal maternal stress and the potential for intervention strategies to support maternal and infant well-being.
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