'C-section, antibiotics, formula milk up babies' health risks'

Babies who are born through Cesarean, exposed to antibiotics and fed on formula milk may have a slow growth and lower diversity of microbes in the first year of life, a new study suggests.
The results centre on the microbiome, the mix of bacterial species that live on human skin and in our guts, and that co-evolved with humans to play roles in digestion, metabolism, and immunity, researchers said.
As rates of children's exposure to C-sections, antibiotic use, and formula feeding have increased in recent decades, the incidence of asthma, autoimmune diseases, and obesity has more than doubled, they said.

Many studies have now linked these trends, but only a few experiments in mice have shown microbial differences to directly increase disease risk, researchers said.
"Our results provide evidence that modern practices change a baby's microbial communities in ways that last through the first year," said Martin Blaser from New York University (NYU) in the US.
"The big, remaining question is whether or not changes in this timeframe, even if resolved later on, affect the founding of microbiomes with lifetime consequences for a child's immune function and metabolism," said Blaser.

Researchers assessed the effects of modern practices on intestinal microbiota development in 43 children, and found multiple changes in the gut microbiomes of the babies based on delivery mode, exposure to antibiotics, and feeding method.

More than 1,000 stool samples were collected monthly from these infants, 24 of whom were born by vaginal delivery and 19 by C-section.
They then used genomic and statistical techniques to analyse the millions of pieces of bacterial DNA in the samples.
The results reflect concepts in ecology such as diversity and dominance of species, researchers said.
The different ways in which babies acquired their original microbiomes, combined with the factors that changed species balance, were found to determine not only bacterial profile, but also which species came to dominate and when, they said.
Researchers found that, compared to vaginally born infants, those delivered by C-section showed significantly greater species diversity in the weeks after birth.

However, these measures declined in cesarean-born infants during their first month, after which they displayed lower diversity up to two years of age. The change in birth mode interrupted the natural interplay between diversity and dominance, said Blaser.
They also found that antibiotic treatment significantly diminished diversity of bacterial species immediately following birth. Diversity then recovered during the first year of life to resemble that of infants not exposed to antibiotics, researchers said.
The findings were published in the journal Science Translational Medicine.