What Is the Main Idea?

From the time they are born, it is important for humans to have a good composition of gut microbes to help with digestion, immune function, and long-term health. However, the method of delivery (vaginal or Cesarean section (C-section)) significantly affects this composition, as described in the free access review article “Impact of Delivery Mode on Infant Gut Microbiota” published in the journal Annals of Nutrition and Metabolism. Based on the review, in this article, we also discuss the potential ways of rectifying the change in composition.

What Else Can You Learn?

What kind of bacteria is seen in vaginally born babies and how does it change in babies born through C-section. Also, what does this mean to the baby’s health in the short and long term?

Importance of the Gut Microbiome

The gut microbiome is the flora of microorganisms (bacteria, fungi, viruses and other microbes) that occupy the digestive tract of the body. These microorganisms have a symbiotic relationship with the human body. The human body gives them a place to thrive, and if the microbes are present in the right composition, they support the host in multiple ways. They help in the digestion of food and in maintaining a healthy immune system. In previous blog posts, we have also discussed its effects on mental health and irritable bowel syndrome.

Of the different microorganisms, the bacterial population is the most well-studied and understood. Where do these organisms come from, though? How do they start populating our gut? Below are some answers based on the recent free access review on the same topic.

The Gut Microbiome in Babies

While currently there is some research evidence that the fetus might already contain some gut microbiome, the most accepted consensus is that babies do not have microbes in their body till they start coming out of the womb. During vaginal delivery, the baby starts taking in the microbes from the mother’s vaginal tract, fecal matter and skin.

Surprisingly, though the gut bacteria composition usually differs between individuals, the bacteria populating babies through the initial years follows a general pattern across countries. All the microbes that they come in contact with during delivery do not necessarily populate in the baby’s body. For example, the vaginal microbes do not have the right conditions to grow in the baby. Even amongst the other microbes, the bacteria that help to digest human milk oligosaccharides like bifidobacteria and Bacteroides are the ones that populate the gut of babies. This is for obvious reasons. The other bacteria that can be pathogenic (cause diseases) are present initially, but their levels go down as the baby ingests more breast milk. Since Bacteroides can live off a wide variety of food (substrates) that we ingest, they are present from birth through adulthood.

Interestingly, the bacteria transferred from mothers during vaginal delivery are seen in the child through their life. So, what happens when a child is delivered via C-section?

Delivery Method Affects the Gut Microbe Composition

While it may not be the first choice of delivery for the mother, often conditions necessitate doing a C-section. With C-section, during the delivery, the baby does not come in contact with the vaginal or fecal microbiome of the mother. This has been shown to alter the gut bacterial composition, especially in the first 6–12 months. The most significant feature is the low quantity of bifidobacteria, almost complete absence of Bacteroides and increased pathogenic bacteria.

These differences between vaginal and C-section delivery mostly level out after 1 year but some researchers found differences in bacterial composition all the way to young adults. More studies have to be conducted to determine the exact long-term effects of this difference in the gut microbiome due to the delivery method.

Impact of Altered Microbiota

Since the bifidobacteria, which breaks down human milk oligosaccharides, is in low abundance in C-section babies, their ability to digest and derive energy from breast milk is lowered. It can also cause the intestinal barrier to be weakened. Combining this with an increased abundance of pathogenic bacteria, the babies can be prone to inflammation, pain and distress. The effect on the immune system can also potentially lead to allergic diseases, obesity and other chronic diseases later in childhood or adulthood.

Ways of Correcting the Disrupted Bacterial Composition

Having understood the changes in microbiome composition, researchers are now working towards finding a solution on how to restore the bacterial composition.

The 3 ways that can potentially work are:

  1. Use of probiotics: Studies showed that probiotics, supplements with live strains of Bifidobacterium and Lactobacillus, successfully improved gut microbiome composition and reduced the incidence of allergic reactions. However, the caveat to this intervention is that it is still not the maternal microbiome.
  2. Breastfeeding: Exclusive breastfeeding was shown to improve the bifidobacterial composition in the gut. In one study where they were supplementing with probiotics, it was seen that along with probiotics, only breastfed babies were able to restore the bifidobacterial composition.
  3. Fecal Microbiota Transfer: In a promising pilot study, the babies were given the mother’s fecal matter (after removing pathogens) diluted in breast milk soon after delivery. This helped restore the complete microbiota composition as seen in vaginal delivery.

The above studies prove to be promising for mothers who are planning C-section or even have to do an emergency C-section. Though many of the studies in restoring the gut microbiota are in the preliminary stages, the mothers should talk to the pediatricians about these and try to implement what is safe and possible for the mother and child. This can benefit the child’s health both in the short and long term.


Note: The author of the paper has declared receiving support from a nutrition institute. It is normal for authors to declare this in case it might be perceived as a conflict of interest. More detail can be found in the Conflict of Interest Statement at the end of the referenced paper.

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