Impact of Maternal Gut Microbiome During Pregnancy

Obesity has become an epidemic in the United States. It is estimated that 41.9% of American adults and 19.7% of American adolescents have obesity, which is defined by a body mass index (BMI) greater than or equal to 30. The connection of obesity to other diseases such as type 2 diabetes, hypertension, cardiovascular disease, kidney disease, non-alcoholic fatty liver disease, and cancer is a major concern.

As a result, research regarding the causes and metabolic effects of this complex disease has been on the rise. A particular area of interest is the relationship between the gut microbiome and metabolism, which could be related to the metabolic dysregulation that is found in obesity. There is evidence that composition of a mother’s gut microbiome has a large impact on fetal metabolism, which could predispose a child to metabolic disorders before birth.

Gut Microbiome and Obesity

Obesity in general has been shown by substantial evidence to have an impact on the gut microbiome. According to a 2018 review article, gut microbiome diversity is decreased in obese individuals compared to non-obese individuals. The balance of various types of bacteria present in the gut is also altered in those with obesity. This can have an impact on the presence of biochemical compounds, which therefore influences an individual’s metabolic health.

Gut microbiota are specifically related to lipid metabolism because they influence the production of HDL, triglycerides, and folic acid. These effects are thought to be mediated by regulation of gene transcription in the host and by production of compounds called short-chain free acids (SCFAs).There is also evidence that a certain species of gut bacteria influences ferritin levels, which are involved in preventing intestinal infection by harmful enterobacteria. There have been some discrepancies regarding which bacteria increase or decrease levels of these various compounds. As a result, further research is needed regarding the exact effect of each particular species and their balance. Although the exact mechanisms are still being studied, it is known that obesity and metabolic dysregulation impacts the gut microbiome.

Maternal Gut Microbiome and Fetal Metabolism

The effects of the gut microbiome are particularly important in pregnancy. Previously, it was accepted that the uterine environment was sterile. Therefore, it was thought that an individual’s gut microbiome developed during the process of birth and throughout early childhood outside of the womb.

However, recent evidence has contradicted this idea. Modern sequencing technology has shown that microbiota and microbial DNA are present in the placenta, amniotic fluid, and umbilical cord during normal pregnancies. This suggests that the fetal gut microbiome is actually developed prior to birth. Therefore, the mother’s gut microbiome has an effect on fetal microbiota, and therefore also on fetal metabolism.

A healthy maternal gut microbiome has been found to be implicated in developing resistance to obesity in offspring through the production of specific SCFAs. SCFAs act on receptors in the sympathetic nervous system, intestinal tract, and pancreas to promote development of these regions. The impact of the maternal gut microbiome is highest in the fetal intestines.This process is vital to maintaining normal fetal glucose metabolism, thermogenesis, and heart rate. A well-balanced, diverse microbiome promotes normal metabolism and has an overall protective effect against obesity.

On the other hand, maternal obesity during pregnancy has detrimental effects on the gut microbiota of both the mother and the fetus. As previously mentioned, obesity has a negative impact on gut microbiome diversity and balance. Since there is evidence that the fetal gut microbiome is developed before birth, the maternal uterine environment is crucial to healthy fetal microbiota and consequently, metabolism. This effect has been demonstrated by large numbers of experiments. For example, offspring of obese mice fed a high-fat diet had significantly lower gut microbiome diversity than offspring of healthy mice. Presumably, a poor intrauterine microbial environment has a negative impact on gut microbiome development. Because of the strong ties between the gut microbiome and metabolism, this proposes a mechanism by which maternal obesity can predispose children to obesity and metabolic dysregulation.

Impact of probiotics

So, how can we ensure that children reap the benefits of a healthy maternal gut microbiome? Probiotics may be the answer.

Research has long established the beneficial effects of probiotics on obesity and metabolic syndrome. Research regarding probiotic supplementation has been done specifically on pregnant women with metabolic disorders. For example, a randomized controlled trial in Iran was conducted on pregnant women with gestational diabetes. The study randomly assigned subjects to receive either an 8-week probiotic supplement consisting of multiple beneficial bacteria or a placebo. At the end of the 2-month period, the probiotic group had improved fasting blood glucose, better insulin sensitivity, and reduced weight gain.

Another study in Finland was done on pregnant women without metabolic disorders and substantiated these results. It revealed that dietary counseling with probiotics reduced risk of both gestational diabetes and central obesity 6 months postpartum. This evidence shows promising potential for probiotics as a management tool for obesity and metabolic dysregulation.

Summary

The gut microbiome is strongly implicated in metabolic regulation. The effects of gut microbiota on metabolism are mediated by production of biochemical compounds, such as SCFAs, which influence numerous pathways to maintain homeostasis. It has also been shown that the infant gut microbiome develops in utero prior to birth, and therefore is influenced by the maternal microbiota. Therefore, a healthy maternal gut microbiome can have powerful protective effects against obesity and metabolic disorders in children. Probiotic supplementation can also be a useful tool to manage obesity and metabolic dysregulation, particularly during pregnancy.