Appearing this week in Canada’s top medical journal, the finding could explain why babies delivered via C-sections are at increased risk of asthma, obesity, inflammatory bowel disease, cancer, diabetes and other illnesses.
The study is based on sophisticated DNA testing of 24 babies born in Winnipeg. After analyzing the babies’ fecal samples, researchers found that infants born by C-section lacked a specific group of bacteria found in babies delivered vaginally.
Babies that were exclusively formula fed also had significant differences in their gut bacteria compared with breastfed babies.
“The infant gut microbiota plays a crucial role in lifelong health,” the researchers write in the Canadian Medical Association Journal Among other things, bacteria prime a baby’s immune system, providing protection against disease-causing organisms.
“We want parents (and physicians) to realize that their decisions regarding C-section and breastfeeding can impact their infant’s gut microbiome and this can have potentially lifelong effects on the child’s health,” first author Meghan Azad, of the University of Alberta, said in a statement released with the study.
In Canada, nearly 27 per cent of all babies are delivered via C-section. Doctors say most surgical births are performed for medically valid reasons. But there are concerns too many C-sections are being ordered because labour isn’t progressing quickly enough, and that to many “routine” but unnecessary interventions are now being done that increase the odds of a woman needing a surgical delivery.
Babies, like all mammals, “are naturally inoculated as they pass through the birth canal,” researchers from the University of Colorado and New York University School of Medicine write in a related commentary.
Yet C-sections are rising globally. In the U.S., more than 30 per cent of babies are now born by caesarean. In China and Brazil, nearly half of babies are born by C-section.
“The human body harbours trillions of microbes, known collectively as the ‘human microbiome,’ ” the Canadian team writes in the CMAJ.
“Some people call it the forgotten organ, because it protects us from pathogens and also helps in the absorption of nutrients,” said Dr. Anita Kozyrskyj, research chair and associate professor of the University of Alberta.
“Increasingly we’re learning that these good bacteria are quite important to the development of the immune system in the infant,” she said. “They train the immune cells not to overreact.”
The gut microbiome is laid down or developed during the first year of life after birth. “We start off with almost a clean slate,” Kozyrskyj said. “During (vaginal) delivery, babies acquire mum’s microbes from her vagina and her GI (gastrointestinal) tract.”
Using DNA sequencing technology, the team found that C-section babies had undetectable amounts of Bacteroides, an important gut bacteria involved in priming the immune system.
