Dr Mette Tollånes, from the University of Bergen and his team studying birth data on more than 1.7 million infants born in Norway between 1967 and 1998 and the medical records of children who had developed asthma by the age of 18 or the year 2002, noted that the percentage of Caesarean section births increased gradually from 1.7% of all births in 1967 to a plateau of 11-12% of all births between 1985 and 1998. Asthma rates also increased over this time.
Further analysis revealed that children born by Caesarean section were, overall, 52% more likely to
develop asthma than those delivered naturally.
For children born between 1988 and 1998, planned
Caesarean section was associated with a 42% increased risk of asthma while emergency Caesarean section was associated with a 59% increased risk, compared with those born naturally.
The researchers suggest that babies born by
Caesarean section are not exposed to their mothers' bacteria during birth, which may be detrimental to the development of their immune systems. Secondly, those born by Caesarean section may have more amniotic
fluid left in their lungs due to a lack of chest compression during birth, which may affect lung health in the long term. However, the team does not rule out other reasons for the association.
More research on the possible causes of asthma
First Published in September 2008
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