Are caesarean babies missing important microbes? New evidence suggests the answer may be no. Recent research published in the journal Cell Host & Microbe shows that mothers are able to transmit microbes to their babies through alternative, compensatory routes. While babies born by cesarean receive fewer of their mother’s gut microbes during birth, they compensate by getting the microbes in their mother’s milk.
Previous research has shown that babies born vaginally have different gut bacteria than babies born via cesarean section. The exact role of the baby’s gut bacteria is unclear, and it is unknown whether these differences at birth have impact on the future health. Scientists at the University of Birmingham’s Wellcome Sanger Institute, UCL, discovered that differences in gut bacteria between vaginally born and caesarean babies largely even out by the age of one.
Caesarean Babies are Supplied with Fewer of the Mother’s Intestinal Bacteria
The gut microbiome is a complex ecosystem of millions of microbes and is considered important for the development of the immune system. Lack of exposure to the right microbes in early childhood has been linked to autoimmune diseases such as asthma, allergies and diabetes. However, it is not fully understood how important the initial gut microbiome is in the development and health of the baby’s immune system, how a baby’s microbiome develops, or what happens to them during different types of birth.
To learn more about the development of the microbiome and whether the method of delivery affects this, the researchers examined 1,679 samples of gut bacteria from nearly 600 healthy babies and 175 mothers. Fecal samples were collected from babies aged four, seven and 21 days, born in UK hospitals by vaginal delivery or caesarean section. Some babies were also followed up later, up to one year of age. Using DNA sequencing and genomic analysis, the researchers were able to see which bacteria were present and found that there was a significant difference between the two delivery methods. They discovered that babies delivered vaginally had far more health-associated (commensal) bacteria from their mothers than babies born by cesarean section. During birth, the baby comes into contact with bacteria from the mother’s intestines. The study found that it was the mother’s gut bacteria that made up much of the microbiome of babies delivered vaginally. Babies born via cesarean section had far fewer of these bacteria. Instead of some of the mother’s bacteria, babies born via cesarean section had more bacteria, which are usually acquired in hospitals, and were more likely to have antimicrobial resistance. Researchers isolated, cultured and sequenced the genomes of more than 800 of these potentially pathogenic bacteria, confirming they were the same strains that caused bloodstream infections in UK hospitals. Although these bacteria don’t usually cause disease in the gut, they can cause infections if they get in the wrong place or if the immune system fails.
Babies born by Cesarean Section Get More Microbes From Breast Milk
While most microbiome research focuses on the gut, the current study should help get a better idea of how the infant microbiome develops in different parts of their body and how it is affected by factors such as delivery mode, antibiotic use and the lack of breastfeeding. To understand how the microbiome develops in the first month of life, the team took 120 Dutch mothers and babies and took repeated samples. They took skin, nasal, salivary and gut microbiome samples from the babies two hours after they were born and when they were one day, one week, two weeks and one month old. The team also collected six different types of microbiome samples from the mothers – Skin, breast milk, nose, throat, feces and vaginal – to determine which of these sources “seed” babies’ different microbiomes. They then analyzed these results in the context of several factors thought to influence microbiome transfer, including delivery mode, antibiotic use, and breastfeeding. Regardless of the mode of birth, the researchers found that about 58.5 percent of a baby’s microbiome comes from their mother. However, different maternal microbial communities contributed to different infant microbiomes. C-section babies received fewer microbes from their mother’s vaginal microbiomes, but—ostensibly to compensate—more microbes from breast milk. This underscores the importance of breastfeeding, which is important for all children but especially for those born through caesarean section.
Ultimately, researchers want to understand how infant microbiome development is related to long-term health. The next step is to investigate whether this early life process influenced by the mother influences not only the short-term risk of infection in the first year of life, but also longer-term health in terms of diseases such as allergies and asthma.
Baby’s Vaccine Responses May be Related to Birth Method
Other research has shown that babies born naturally have higher levels of antibodies than those born by caesarean section after they have received their vaccinations, which protect against bacteria that cause lung infections and meningitis. Researchers from the University of Edinburgh studied the relationship between gut microbes and post-vaccination antibody levels in a cohort of 120 babies vaccinated at 8 and 12 weeks for lung infections and meningitis. The researchers tracked the development of the gut microbiome – the microbial community that lives in our bodies – during the child’s first year of life and its immune response to the vaccines by testing saliva samples at 12 and 18 months of age.
Of the 101 babies tested for antibodies as a result of the vaccine, which protects against lung infections, the researchers found antibody levels in babies born naturally were twice as high as those born by caesarean section. Breastfeeding was associated with 3.5 times higher antibody levels than in naturally born infants who were formula-fed. 66 babies were tested for antibody levels as a result of the vaccine, which protects against meningitis. Experts found that regardless of breastfeeding, naturally born babies had antibody levels 1.7 times higher than those born by cesarean section. The team concludes that the microbiome of babies early in life contributes to the immune system’s response to the vaccines and determines the level of protection against certain childhood infections. According to the experts, vaccination schedules could also be adjusted in the future based on the type of birth or an analysis of the baby’s microbiome. The research was published in Nature Communications.