Researchers in the Netherlands followed children up to the age of eight and found that those born by caesarean section were almost 80 per cent more likely to develop asthma.
Caesareans further asthma link
The researchers suggested increases in caesareans may have contributed to the rise in asthma in industrialised countries.
Previous studies reported mixed results, but varied in definition of asthma and in age of children at diagnosis.
What is the research?
Dr Caroline Roduit, of the National Institute for Public Health and the Environment in the Netherlands, and colleagues followed 2,917 children from birth to the age of eight.
They found that 20.2 per cent of those born by caesarean section had developed asthma, compared with 11.7 per cent of those born by vaginal delivery.
This represented a 79 per cent increased relative risk of developing asthma. The risk of asthma following caesarean section increased if children had parents with allergies.
How caesareans may increase asthma risk is not clear, the researchers said. Children born by caesarean have been shown to have differences in intestinal colonisation, which could affect their immune responses.
Asthma is also known to be associated with sensitisation to certain allergens, they added. So children born by caesarean section may be at higher risk of sensitisation, and therefore to asthma, they suggested.
What do the researchers say?
'Our results emphasise the importance of gene-environment interactions on the development of asthma in children,' Dr Roduit and her team said.
'The increased rate of caesarean section is partly due to maternal demand without medical reason. Mothers should be informed of the risk of asthma for their child, especially when the parents have a history of allergy or asthma.'
What do other researchers say?
Asthma UK stressed the conflicting results of previous studies investigating the link between asthma and caesareans.
Dr Mike Thomas, the charity's chief medical adviser, said: 'This study builds on evidence indicating that birth by caesarean section may increase the risks, particularly in children whose parents have asthma or allergies.'
He added: 'Sometimes a caesarean is needed for medical reasons, but where possible a natural birth is better.'
- Children born by caesarean have greater asthma risk.
- The risk is increased for children whose parents have allergies.
- Women should be informed if they consider elective caesarean.
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