In an article published within the journal Current Opinion in Microbiology, scientists have provided an in depth overview of the aspects affecting maternal gut microbiota while pregnant and its impact on maternal and infant health.

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Background

Pregnancy is related to a wide selection of hormonal, immunological, and metabolic changes needed for fetal development. Essentially the most notable changes include increased cardiac output, higher levels of T regulatory cells, and alteration in gut microbiome composition.

Alteration in gut microbiota composition and variety is related to changes in women’s metabolic, immunological, and neurological processes, no matter pregnancy status. As well as, changes in gut microbiota composition are known to affect insulin sensitivity. In children with type 1 diabetes, functional and metabolic changes in gut microbiota have been documented.

Alteration in gut microbiota while pregnant

Only limited evidence is obtainable to thoroughly understand the changes in gut microbiota while pregnant and its impact on maternal and fetal health. Nevertheless, in accordance with the available literature, low-grade inflammation on the intestinal mucosa in addition to hormonal changes, could be accountable for gut microbiota alteration while pregnant.

Regarding hormonal changes, pregnancy-related induction in progesterone levels is thought to directly associate with increased Bifidobacterium levels in women. Bifidobacterium is a useful bacterium that naturally resides within the intestine. Due to this fact, the gut-to-gut transmission of this bacterium from the mother to the infant is crucial throughout the neonatal period. In infants, this bacterium helps degrade human milk oligosaccharides coming from maternal milk, along with developing infant gut microbiota and immune system.

Aspects influencing maternal gut microbiota while pregnant

Adult human gut microbiota might be influenced by many aspects, including body mass index (BMI), medications, diseases, environment, and lifestyle (food plan, physical activity, smoking, and drinking habits). Pre-pregnancy exposure to those aspects can result in structural and functional alteration in maternal gut microbiota while pregnant.

Animal studies have shown that maternal food plan influences maternal and infant gut microbiota composition before and while pregnant. Each pre-pregnancy body weight and pregnancy-related weight gain have been found to change the composition and variety of maternal gut microbiota.

Infant gut microbiota are influenced by the best way they’re delivered. For instance, infants delivered vaginally have been shown to achieve useful changes in gut microbiota in comparison with those delivered by c-section.

Functional studies in animals have shown that smoking-related nicotine exposure while pregnant affects maternal gut microbiota, which in turn alters fetal exposure levels to circulating short-chain fatty acids and leptin during in-utero development.

Certain diseases before pregnancy, reminiscent of inflammatory bowel disease, have been found to influence maternal microbiota while pregnant. The microbiota of the pregnant mother’s gut has also been shown to be affected pre-pregnancy and while pregnant by certain medications, including antibiotics, proton-pump inhibitors, metformin, laxatives, and probiotics.

Maternal health impact of altered gut microbiota

Studies have found maternal gut microbiota alteration while pregnant is related to pregnancy complications, including gestational diabetes and preeclampsia.  

Gestational diabetes

A spontaneous induction in blood glucose levels while pregnant is medically termed gestational diabetes. Studies have shown that a reduced abundance of useful bacteria and an increased abundance of pathogenic bacteria are accountable for the onset of gestational diabetes.

Within the microbiome of gestational diabetes patients, an increased abundance of membrane transport, energy metabolism, lipopolysaccharides, and phosphotransferase system pathways has been observed. Recent evidence indicates that gut microbiota-derived dopamine deficiency within the blood, impaired production of short-chain fatty acids, and excessive metabolic inflammation are collectively accountable for the event of gestational diabetes.

Preeclampsia

Preeclampsia is characterised by new-onset hypertension, proteinuria, and organ dysfunction while pregnant. Studies involving pregnant women with preeclampsia have found gut microbiota dysbiosis (imbalance in gut microbiota composition) and increased plasma levels of lipopolysaccharide and trimethylamine N-oxide.

Recent evidence indicates that preeclampsia onset is related to reduced bacterial diversity in gut microbiota. Specifically, the changes in gut microbiota include a depletion in useful bacteria and an enrichment in opportunistic bacteria.

Some mechanistic studies have identified that gut microbiota dysbiosis induces immune imbalance and intestinal barrier disruption in pregnant women, resulting in the translocation of bacteria to the intrauterine cavity, placental inflammation, and poor placentation. All these aspects collectively contribute to the event of preeclampsia.

Infant health impact of altered gut microbiota

Alteration in maternal gut microbiota has been found to affect the fetus’s neurodevelopment via signaling microbially modulated metabolites to neurons within the developing brain. These changes can have long-term effects on an infant’s behaviors.

Maternal microbiota-derived metabolites reminiscent of short-chain fatty acids are known to shape the metabolic system of infants. Some evidence has also indicated that maternal gut microbiota influences an infant’s susceptibility to allergic diseases.