03 October 2011

Allergies linked to babies' birthplace

Where and how a baby is born might affect its chances of getting allergies and asthma growing up, suggests a new study.


Where and how a baby is born might affect its chances of getting allergies and asthma growing up, suggests a new study.

Researchers found that babies were more likely to harbour Clostridium difficile in their intestines if they were born in the hospital, and especially by caesarean section – and those bacteria were tied to a child's chances of later getting allergies or asthma.

"Our message is not that mode nor place of delivery decisions should be based on the potential risks on developing allergic diseases," study author Dr John Penders, from Maastricht University in the Netherlands told Reuters Health in an email.

But, researchers said, it's one more topic to add to a growing list of potential culprits behind the recent increase in asthma and allergies in kids.

Faecal samples tested

The study included about 2,700 babies who were followed until they were seven years old.

One month after birth, the researchers tested faecal samples from infants, looking to see whether their intestines were hosting a few specific species of bacteria, such as Escherichia coli and C. difficile.

When kids were older, Dr Penders' team asked parents to report how often the children wheezed and needed asthma medications, and whether they had recently had eczema. Kids also had blood tests to see if they were sensitized to certain foods or pets.

The researchers found that C. difficile was most commonly seen in the intestines of babies born by caesarean section. Forty-three percent of them harboured C. difficile in their faeces, compared to 27% of babies born vaginally in the hospital and 19% of those born at home.

Asthma, eczema, food sensitisation

And, kids who tested positive for C. difficile as babies were twice as likely to have asthma at age six or seven, and were also more likely to have eczema or a food sensitisation.

In all, about 7% of kids had asthma, close to 22% had a food sensitisation and 12% recently had eczema.

Dr Penders and his colleagues proposed in the Journal of Allergy and Clinical Immunology  that a particular balance of gut microbes may predispose certain kids to asthma and allergies – although their study can't prove that one causes the other.

Peter Dr Bager, who has studied delivery and allergy risks at the Statens Serum Institute in Copenhagen, Demark, said that would fit in with the hygiene hypothesis.

Many factors involved

Having a skewed mix of gut bacteria species early on, especially lacking a diverse range of bacteria, "reduces the early stimulation of the immune system," which could lead to more allergies later on, said Dr Bager, who was not involved in the new research.

But Dr Ruchi Gupta, an allergy researcher from Children's Memorial Hospital in Chicago who also was not involved in the study, said it's hard to interpret too much from the findings. "There are so many factors that go into a child's development of allergies and asthma," she told Reuters Health.

"Although I think the results are interesting, I think they're a first step," she said, adding that more investigation is needed into the possible link between gut microbes and allergies.

"We cannot conclude that this specific bacterium (C. difficile) is the cause of the increased risk of allergies and asthma," Dr Penders added. "The microbiota contains thousands of different species and we only measured a few of them."

(Reuters Health, October 2011) 

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