Babies born via c-section are more likely to become obese than those born naturally, a study has revealed.
Research from New York University found that mice born via a c-section are more likely to have an unbalanced amount of good and bad bacteria in their stomachs, which puts them at risk for gaining too much weight.
For the study, researchers observed 34 mice that were delivered by c-section and 35 mice that were born naturally.
They tracked their body weights and analyzed their intestinal bacteria until the mice had grown into adults.
The human gut has more bacteria than any other part of the body, both in number and diversity.
There are four major types of gut bacteria: Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria.
Firmicutes play a role in energy re-absorption, and may be linked to diabetes and obesity.
Bacteroidetes account for 30 percent of all gut bacteria, and are important to our ability to digest and use energy from carbohydrates and sugars.
Acinobacteria produce bioactive metabolites, which we use in medicines like antibacterials.
Proteobacteria are a category of bacteria that include diseases like chlamydia, but exist in healthy guts.
Mice that were born via a c-section put on about 30 percent more weight than their counterparts who'd had a natural birth.
Females, specifically, who had been delivered by c-section had gained a staggering 70 percent more weight than the mice born vaginally.
The drastic increase is credited to a difference in the bacteria found in the stomachs of the two groups of mice.
The microbiome, which houses such bacteria, in mice born vaginally progressed normally throughout the course of the study.
However, that of mice born by c-section, matured too quickly at first and then regressed later in their lives.
Study author Dr Maria Dominguez-Bello said: 'Our study is the first to demonstrate a causal relationship between c-section and increased body weight in mammals.'
The research team said that c-sections, while critical in about 15 percent of births, are widely overused, citing that 50 percent of births in Brazil, Iran and the Dominican Republic are performed via the operation.
They are hopeful that their work will curb unnecessary cesareans and bring down the growing obesity rate in the US.