The rise in asthma in industrialised countries over the past 30 years may have been driven by an increase in Caesarean births, researchers report.
Babies born by Caesarean delivery are more likely to develop asthma than those delivered naturally, doctors say. Exposure to bacteria in the vagina during birth is thought to play a key role in priming the immune system, providing a defence against the development of allergies. In Caesarean children, exposure to bacteria happens later and research has shown they have different intestinal flora – gut bacteria – suggesting the maturation of their immune systems is delayed.
A study of 3,000 children in the Netherlands who were followed until they were eight years old showed those born by Caesarean delivery were 80 per cent more likely to have developed asthma than those delivered traditionally. Among the one in 10 children with two allergic parents, the incidence of asthma was three times higher among those born by Caesarean. These children have a strong inherited predisposition to the disease.
Caesarean rates have risen from 5 per cent of all births in the 1970s to more than 30 per cent in some regions of the world, as doctors have sought to reduce the risks of childbirth. In the UK the current Caesarean rate is around 22 per cent of all births.
Over the same period, asthma rates rose strongly until the mid-1990s. Official figures show the prevalence has since remained stable in many European countries, but some experts have disputed the accuracy of the data and claimed the condition is still increasing but the definition has changed.