June 18, 2022 10 min read
Over the past decade, research has established an undeniable link between the human gut and overall physical and mental health.
Our gut health not only relies on the number of microorganisms but also on the ratios in which they are present in our gastrointestinal tract. These microorganism populations are collectively known as the gut microbiome (1).
The foundation of the microbiome is established in the womb (Younge et al., 2019), followed by dramatic restructuring and reorganization throughout the first 2-3 years of life. While reaching homeostasis, this developing gut microbiome will eventually support our life-long ability to fight off diseases (2).
Given that this primitive fetal microbiome plays a crucial downstream role in our overall health, moms-to-be are asking more specific questions about gut health during pregnancy.
In this article, we will explain the normal changes in the gut microbiome during pregnancy: what factors could negatively impact gut health and what the outcome might be during pregnancy and after birth.
Pregnancy is one of the most highly complex and dramatic physiological processes for the female body to endure. Through a range of highly complex modulations, the maternal body develops the ability to aggressively defend the fetus against external threats, while maintaining a hospitable, tolerant environment towards the fetus at the same time!
These modulations involve significant hormonal and metabolic shifts that can have a dramatic impact on the gut microbiome and immune system (3).
In fact, during a healthy pregnancy, the mother’s gut microbiome shifts towards high levels of microbes involved in energy production and storage, like Akkermansia, Bifidobacterium, and Firmicutes. Simultaneously, Proteobacteria and Actinobacteria populations increase to act as pro-inflammatory bacteria for protecting the mother and fetus from infections (4).
This maternal gut microbiome composition during pregnancy goes on to serve as the foundation for the baby’s own gut microbiome. This primitive microbiome is initially transferred from the mother to the fetus while in the womb (5) and is further supplemented by microbial transfer from mother to baby during vaginal delivery and breastfeeding (6).
Although gut dysbiosis during pregnancy is a normal and beneficial part of the gestation period, several factors can contribute to dysbiosis with detrimental effects.
Here are some of the main factors that can sway gut reorganization towards an unhealthy and sometimes dangerous outcome during pregnancy:
The link between maternal diet during pregnancy and the gut microbiome of infants is well-established (7).
Although feeding studies in pregnant women are controversial and not readily undertaken, food and diet questionnaires have revealed important clues about this link.
A diet high in fat causes the depletion of beneficial gut bacteria in pregnant mothers. Lower levels of beneficial bacteria were also present in their offspring at 6 weeks old (8).
Further studies also showed that 6-week-old infants could be classified according to their gut microbiomes that were strongly correlated to their mothers’ intake of fruit and dairy products during pregnancy (8).
Unfortunately, a poor or unhealthy maternal diet is further challenged by the changes in eating habits brought on by persistent morning sickness, food cravings, and aversions associated with pregnancy.
Even before becoming pregnant, obesity contributes to some potentially bleak outcomes for women who plan to have children (9).
A high Body Mass Index (BMI) before pregnancy has been conclusively established as a marker for maternal obesity and excessive weight gain during pregnancy. These factors also have a profound impact on the maternal gut microbiome.
Obese pregnant women typically display gut dysbiosis characterized by lower populations of beneficial Bifidobacterium and Bacteroides species with higher populations of pro-inflammatory Escherichia coli, compared to lean expectant mothers.
Overall, maternal obesity also caused lower microbial diversity. The potential role that maternal obesity plays in pregnancy and beyond is summarized in figure 1 below.
Figure 1. Overview of the role of gut microbiota in the effects of maternal obesity during pregnancy on offspring metabolism (directly from Zhou & Xiao, 2018).
Stress is one of the dominant culprits in causing gut dysbiosis in otherwise healthy adults.
The maternal microbiome is no different.
Research revealed that mothers who experience significant stress levels during pregnancy have an altered gut microbiome composition and diversity. These results showed that stress disrupted the normal microbiome shift that takes place during pregnancy and this altered microbiome can be transferred to their babies (10).
Although moms-to-be may have some level of control over the stress they are exposed to during pregnancy, sadly, exposure to stress is not always within our control.
Early life stress that may include emotional, physical, or sexual abuse, low socioeconomic status, or even chronic household dysfunction, has been found to change the way the body is programmed to respond to stressors later in life.
Women who experienced multiple life stress events in early childhood were found to have an altered gut microbiome composition and inflammation levels during pregnancy (11).
Gestational diabetes is a condition caused by ineffective insulin responses that lead to elevated glucose levels in a mother’s blood during pregnancy. If untreated, gestational diabetes could lead to a range of pregnancy complications including premature or stillbirth.
Studies have consistently shown a link between gut dysbiosis and the development of gestational diabetes (12).
Women who developed gestational diabetes were found to have significant gut dysbiosis at various stages of their pregnancy.
Changes in gut microbial populations that were consistently linked to gut dysbiosis were an increase in Ruminococcaceae, Enterobacteriaceae, Desulfovibrio, Parabacteroides distasonis, Prevotella, and Collinsella. Furthermore, Faecalibacterium and Bifidobacterium populations were typically lower.
Pre-eclampsia is a condition in which pregnant women develop dangerously high blood pressure that can have fatal repercussions for mom and baby.
Research studying the impact of gut dysbiosis during pregnancy on the risk of developing pre-eclampsia is limited. However, isolated studies have revealed a unique microbial profile in pregnant women with pre-eclampsia when compared to healthy pregnant women.
These microbial profiles included the reduction of beneficial Faecalibacterium and Akkermansia populations with simultaneous increases in Fusobacterium and Veillonella (13).
Babies who are born preterm are typically delivered before 37 weeks of gestation. Depending on how early in pregnancy the baby is born, some complications may include difficulty regulating body temperature, an immature respiratory tract, and an inability to feed on their own. Many of these complications require medication, intensive care, and/or surgeries to sustain life.
Traditionally, preterm birth was mostly thought to be the result of reproductive tract infections during pregnancy. However, a study compared both the vaginal microbiomes and the gut microbiomes of mothers who suffered a preterm birth with those who delivered at full term.
Interestingly, there were no significant differences between their vaginal microbiomes, but rather a significant difference when comparing their gut microbiomes.
Mothers who have preterm births had lower levels of Clostridium and Bacteroides species and higher levels of Lactobacilliales than those who delivered full-term babies (14).
Elements of the maternal gut microbiome serve as the foundation for the gut microbiome of offspring. As a result, gut dysbiosis during pregnancy could transfer from mom to baby with permanent adverse effects.
In fact, it is widely accepted that the early infant microbiome and its initial development affect the likelihood of developing diseases throughout their lifespan. Some of these diseases include food allergies, obesity, and inflammatory bowel disease (15).
Furthermore, a person’s microbiome composition plays a pivotal role in their life-long ability to ameliorate and cope with stress.
Research has even revealed that maternal gut dysbiosis impacts the cognitive development and reasoning skills of their children at preschool age (16).
There are numerous ways to support gut health that could dramatically improve the physical and mental well-being of women and their future pregnancies.
Here are a few ideas to get started:
It is well known that long-term dietary habits have a strong impact on the composition of microbiota in our gut (17).
A balanced diet that includes foods rich in fermentable fiber holds the potential to induce a more beneficial microbiome.
To learn more about a gut-healthy diet, continue reading here.
Aside from seeking professional help in the form of psychotherapy and avoiding known stressors, exercise, yoga, and breathing exercises have shown positive effects on our perception of stressful situations.
This stimulation supports the communication network between the gut and brain which in turn aids in achieving gut homeostasis. Studies showed that this can be accomplished through breathing exercises, humming, and gargling (18).
Prebiotics contain live beneficial gut microorganisms that aid in supplementing your gut microbiome towards homeostasis.
Beneficial bacteria in our gut need prebiotics to survive and thrive. Prebiotics are found in high-fiber foods and are not readily broken down in our digestive system. These prebiotics rather serve as food for the beneficial microbes (probiotics) in the gut.
To find out more about pre and probiotics, continue reading here.
Although pregnancy may not be the right time to make dramatic changes to health and lifestyle habits, there are many ways to still make a positive impact on maternal gut health under medical supervision.
Much like before pregnancy, the gut microbiome could benefit from a healthy, balanced diet, stress management practices, and possible supplementation with prebiotics or probiotics. However, the approval from your doctor is MUST if you decide to take any supplements during pregnancy.
An infant’s gut microbiome will depend on how they were born.
Vaginally delivered infants who had contact with their mother’s birth canal show microbiome profiles with Lactobacillus, Bacteriodes, Bifidobacterium, Prevotella, Escherichia, and Streptococcus.
In contrast, infants delivered via Cesarean section have gut microbiome profiles reflecting the skin microbiome of their mothers. These populations are dominated by Staphylococcus with reduced proportions of Bifidobacteria and Bacteroides.
Regardless of the mode of delivery, the microbiome of an infant is highly plastic and their early diet forms a crucial part of their gut colonization. The aim is to stimulate an increase in Bacteroides, Bifidobacterium, and Lactobacillus species as part of the development of an infant's early immune system.
For example,Bifidobacteria infantis stimulate cellular differentiation in the intestinal surface that helps protect against infections.
Simultaneously, Bacteroides fragillis and Clostridia species stimulate cell differentiation that influences the development of immune responses (19).
Aside from the dramatic shifts that take place in the maternal gut microbiome during pregnancy, several factors render the gut vulnerable to dysbiosis as a result of poor diet, obesity, and stress.
Gut dysbiosis could result in detrimental pregnancy complications like gestational diabetes, pre-eclampsia, and preterm birth. After birth, maternal gut dysbiosis could impact the gut microbiome of the offspring, their metabolism and chances of becoming obese, and their overall ability to fight diseases.
There are, however, positive steps that can be taken to improve gut health and avoid these potentially negative outcomes before and during pregnancy.
Following a balanced diet, managing stress levels, and supporting gut health through pre and probiotic supplementation are among the proven strategies to combat maternal gut dysbiosis under medical guidance.
Kari du Plessis, Ph.D. in Biotechnology, who enjoys writing about holistic health topics.
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