Being born by Caesarian section may increase the risk of obesity in mice, a new study said Wednesday.
That's probably because the procedure changes a body's microbiome, the set of bacterial species living in the human gut, according to the study published online in the U.S. journal Science Advances.
While C-section is a life-saving practice -- needed in 10 to 15 percent of births to avoid risking the life of mother or child -- this delivery mode is often overused, with some regions using C-sections in more than 40 percent of births.
Concurrent with an increase in C-section births, obesity and immune-related diseases including type 1 diabetes, allergies and celiac disease are also on the rise.
What's more, preventive antibiotics, which are used in C-sections, have also been related to increased risk of these modern diseases.
To further investigate the impacts of C-sections on weight gain and gut microbiota during early development, Maria Dominguez-Bell at New York University and her colleagues compared 34 mice delivered by C-section with 35 control mice born vaginally.
The researchers followed body weight and used genomic techniques to analyze intestinal bacterial DNA from newborn pups through development and into adulthood.
They found mice born by Caesarian section gained on average 33 percent more weight in the 15 weeks after weaning than mice born vaginally, with females gaining 70 percent more weight.
Along with higher weight, mice born by C section had significant differences in bacterial species in their guts when compared to those born vaginally, and regardless of gender.
The microbiome structure of mice born vaginally matured normally over the course of the study, but in mice delivered by C-section, microbiome structure matured too soon initially, but then became relatively immature later in life.
"Our study is the first to demonstrate a causal relationship between C-section and increased body weight in mammals," said Dominguez-Bello.
The current study indicated that microbiota transmitted from mothers to vaginally born pups provided protection against weight gain.
Bacterial groups found to dominate in pups delivered vaginally, including Bacteroides, Ruminococaceae, and Clostridiales, had been previously linked to leaner body type in mice, according to the researchers.
"Further research is needed to determine whether the dominance of certain bacterial groups can protect against obesity," said Dominguez-Bello. "Our results support the hypothesis that acquiring maternal vaginal microbes is needed for normal immune and metabolic development."