Prenatal maternal stress is commonly associated with many health problems in the newborns and infants, although the exact mechanism is not clear. Several studies focused on this aspect particularly, related to maternal stress and infant gut health, and found a possible link. So, is prenatal stress associated with infant gut microbes?
Prenatal maternal stress has always been a concern for the health of the mother as well as the child. It is thought to be linked with several psychological functioning and behavior of the infant. Recent studies have focused on finding if prenatal stress is associated with infant gut microbial composition, which can affect infant health.1 The results suggested a possible mechanism by which maternal stress could influence offspring development. This may pave the way for a potential bacterial intervention to improve the health and development of infants in pregnant women having stress.
Let us understand this in detail.
Is Prenatal Maternal Stress Associated With Infant Gut Microbes?
Chronic stress in pregnancy and increased levels of cortisol levels in pregnant women have been linked to alterations in gut microbes in infants. Several studies done earlier too have pointed towards the possible link. To understand if prenatal maternal stress is associated with infant gut microbes, it is important to consider these findings.
According to a study report, maternal prenatal psychosocial stress is associated with altered child emotional and behavioral development. A possibly underlying mechanism suggests that prenatal psychosocial stress affects the child through the mother’s and the also the child’s intestinal microbiota.2 In this study the association between maternal pregnancy general anxiety and microbial composition, which provided evidence of a mechanism through which psychosocial symptoms in pregnancy could affect the offspring and their gut microbes.
It is necessary to understand the reason behind infant gut involvement and its importance. Some studies suggest that the colonization of the gut with microbes in early life is crucial to the development of the immune system, metabolic functions, and future health of the newborns. Maternal microbes are transferred to the offspring during childbirth, which is a key step in the colonization of the infant’s gut.3 According to the studies done on infant meconium, it is noted that bacteria are present in the fetal gut even before the birth, which means that colonization could occur prenatally. Although prenatal transmission of microbes to the fetus is seen in animals, which hints at the same possibility in humans, direct evidence of utero transfer in humans is not available. More studies focusing on the same and studies targeting colonization of the fetal gut in utero would be instrumental in giving a better understanding.
What Do Recent Studies Say About Prenatal Maternal Stress Associated With Infant Gut Microbes?
Is prenatal stress associated with infant gut microbes? Keeping in view the results from animal studies, a recent study was conducted to understand the maternal prenatal stress and its association with developmental outcomes.
According to the reports from FinnBrain research project of the University of Turku, Finland, maternal prenatal psychological distress and hair cortisol levels associate with infant fecal microbiota composition at 2.5 months of age.4
It is believed that alterations in the composition and function of the infant intestinal microbiota may mediate some of the observed health effects. This was based on a viewpoint that showed that exposure to prenatal stress can modify the offspring’s intestinal microbiota. In this recent study, the researchers aimed to investigate the associations between maternal prenatal psychological distress (PPD) and hair cortisol concentration (HCC) with infant fecal microbiota composition in a large prospective human cohort.
The study used hair cortisol analysis, due to which it was possible to measure the concentration averages of stress hormone cortisol over several months. The symptoms of the mother were assessed three times during the pregnancy. The infant gut microbiota was analyzed at the age of 2.5 months with next-generation sequencing.5
According to the study, they found evidence that infants with low levels of exposure to maternal PPD had increased abundances of potentially health-promoting bacteria including Akkermansia. At the same time, it was interesting to know that infants exposed to low levels of maternal HCC had increased abundances of Lactobacillus.
Intervention studies have reported that probiotic treatments with Bifidobacterium and Lactobacillus species can alleviate self-reported distress and affect cortisol excretion. These findings are in line with a previous human study which indicated that lactic acid bacteria abundance may serve as a potential marker for healthy infant microbiota and optimal prenatal conditions regarding PPD.
Also, it was found in this study that there is an association between the maternal early and mid-pregnancy HCC and the members of infant fecal microbiota. The existing associations were partially similar to those found between maternal chronic PPD symptoms and the infant fecal microbiota.
In short, the results of this study confirmed that maternal chronic PPD showed positive associations with bacterial genera from phylum Proteobacteria, with potential pathogens in infants. Also, chronic PPD was associated negatively with Akkermansia and Lactobacillus. Nither of maternal chronic PPD nor HCC was associated with infant decal microbiota.
Other studies too had suggested a potential mechanism linking maternal PPD with infant fecal microbiota. In this study, it was reported that maternal depressive symptoms are associated with reduced fecal secretory IgA contents in infants. As IgA is an important factor in immunity, it also plays a crucial role in the modulation of bacterial colonization in the gut. The studies suggest maternal stress could result in immune-dysregulation and resulting IgA depletion in the infant gut, which could raise Proteobacteria.
Although these are found in the gut, Proteobacteria also contain species that can cause inflammation in the body. These can impact the health of the child and may be linked to disease risk in the future. As the present study does not explain the relationship between prenatal maternal stress and gut microbes related to immune system function, further research is needed to understand this.
However, the present study concludes that chronic maternal PPD symptoms and raised HCC are associated with alterations in infant intestinal microbiota composition.4 This clearly states that there is an increased possibility that prenatal stress is associated with infant gut microbes. As the earlier literature too supported that maternal PPD symptoms were associated with increased genera from Proteobacteria phylum. Further studies are required to understand how these microbiota changes may be linked with child health outcomes in later life.