Unlike babies born through vaginal delivery, those born by cesarean delivery are not exposed to critical gut microbes, potentially setting back their immune system. This is evidenced by results of a recent study, published in the journal Nature Microbiology, which found that a single dose of the measles vaccine is more than twice as likely to be completely ineffective in cesarean-born children, compared with those born vaginally.

Wang W, O'Driscoll M, Wang Q, et al. Dynamics of measles immunity from birth and following vaccination. Nat Microbiol. Published online May 13, 2024.

 

 

 

Reduced immunity in C-section delivery

 

How we are born “has long-term consequences on our immunity to diseases as we grow up,” said senior author of the Nature Microbiology study, Henrik Salje, PhD, in a University of Cambridge​ press release.

University of Cambridge. Birth by C-section more than doubles odds of measles vaccine failure [press release]. May 13, 2024.

 

An increasing number of birthing parents around the globe choose cesarean deliveries. During cesarean delivery, children miss direct contact to the birthing parent’s microbiome that occurs with a vaginal delivery, which may lead to an altered immune development.

Research suggests the microbes that “seed” the intestine during delivery may “lead to changes in long-term colonization,” according to authors publishing in Clinics in Perinatology.

Neu J, Rushing J. Cesarean versus vaginal delivery: long-term infant outcomes and the hygiene hypothesis. Clin Perinatol. 2011 Jun;38(2):321-31. doi: 10.1016/j.clp.2011.03.008. PMID: 21645799; PMCID: PMC3110651.

 

“We think this means they take longer to catch up in developing their gut microbiome, and with it, the ability of the immune system to be primed by vaccines against diseases including measles,” said Dr. Salje in the press release.

 

Evidence from measles vaccination study

 

In looking at the efficacy of the measles vaccination in those children born via C-section, we can see the effects of not being exposed to the microbiome of the birthing parent.

Cesarean deliveries were linked with a 2.56 (95% confidence interval: 1.06–6.37) increased odds of a failed immune response to the first measles vaccination dose.

Wang W, O'Driscoll M, Wang Q, et al. Dynamics of measles immunity from birth and following vaccination. Nat Microbiol. Published online May 13, 2024.

Specifically, primary vaccine failure occurred in 12% of those born via cesarean delivery and in 5% born by vaginal delivery. But the second vaccine dose induced robust immunity against measles in those born by cesarean delivery.

 

“We know that a lot of children don't end up having their second measles jab, which is dangerous for them as individuals and for the wider population,” Dr. Salje said. “Infants born by C-section are the ones we really want to be following up to make sure they get their second measles jab, because their first jab is much more likely to fail.”

“Available epidemiological data show that atopic diseases appear more often in infants after cesarean delivery than after vaginal delivery,” note the Clinics in Perinatology authors.

Neu J, Rushing J. Cesarean versus vaginal delivery: long-term infant outcomes and the hygiene hypothesis. Clin Perinatol. 2011 Jun;38(2):321-31. doi: 10.1016/j.clp.2011.03.008. PMID: 21645799; PMCID: PMC3110651.

“The composition of enteric microbiota in early days of life seems [...] to be a very important factor for achieving and maintaining good health in the years to come.”

 

Research also shows a “delayed onset of lactation with cesarean section. [These infants] also lacked the early support of breast milk as stimulator for a physiological intestinal flora. Both the nonphysiological start of colonization and the missing early dietary support by delayed start of lactation might result in these long-lasting effects,” the authors concluded.

 

Vaginal microbiota transfer 

 

They exposed 68 cesarean-delivered newborns to maternal vaginal fluids or saline. Shortly after delivery, the babies’ mouths and bodies were swabbed each with gauze soaked in saline or in the birth parents’ vaginal fluid. Six weeks later, samples of the babies’ stools were studied for fecal microbes.

Zhou L, Qiu W, Wang J, et al. Effects of vaginal microbiota transfer on the neurodevelopment and microbiome of cesarean-born infants: A blinded randomized controlled trial. Cell Host Microbe. 2023;31(7):1232-1247.e5.

López Lloreda C. Swabbing C-section babies with mom’s microbes can restore healthy bacteria. Science. June 15, 2023.

 

The results, published in Cell Host & Microbe, showed that within 42 days after birth, vaginal microbiota transfer “accelerated gut microbiota maturation and regulated the levels of certain fecal metabolites and metabolic functions, including carbohydrate, energy, and amino acid metabolisms,” the authors said.

Zhou L, Qiu W, Wang J, et al. Effects of vaginal microbiota transfer on the neurodevelopment and microbiome of cesarean-born infants: A blinded randomized controlled trial. Cell Host Microbe. 2023;31(7):1232-1247.e5.

The adverse events did not differ between the groups.

 

The authors concluded that vaginal microbiota transfer “is likely safe and may partially normalize the fecal microbiome in cesarean-delivered infants.”