Asthma Risk Rises After Caesarean Birth

Babies born by caesarean section are more prone to asthma than babies delivered normally, suggests research just published.

The news has been revealed today - ahead of print in the specialist journal 'Thorax' - and has emerged from a study of 3,000 children, whose respiratory health was monitored until they reached the age of eight.

By the time the children were that age, 362 (12.4%) had been diagnosed with asthma for which they had been prescribed inhaled steroids.

Just 8.5% (247) children had been born by caesarean section, but they were almost 80% more likely to have been diagnosed with asthma than their vaginally delivered peers.

The association was even stronger for the 9% of children with two allergic parents and therefore a strong inherited predisposition to the disease.

They were almost three times more likely to be asthmatic by the time they were 8, compared with children whose parents were not allergic, who were around 36% more likely to have this diagnosis.

Rates of asthma have soared in industrialised countries in parallel with a rise in caesarean section births, which have increased from 5% in the 1970s to more than 30% in 2000.

The authors say that the link between caesarean section births and an increased risk of asthma may lie in the timing of the priming of the immune system: caesarean delivery delays exposure to microbes, they said.

Previous studies investigating the link between asthma and caesarean delivery have produced conflicting results.

But the authors said that the number of children included in the study, the long monitoring period, and the definition of asthma to include inhaled steroids, strengthens their findings.

"The increased rate of caesarean section is partly due to maternal demand without medical reason," said the authors, adding that mothers should be informed of the risk of asthma for her child, especially when the parents have a history of allergy or asthma.

(BMcC)