Caesarean babies at higher asthma risk
Reported June 21, 2008
Babies born by caesarean section are up to 50 per cent more likely to develop asthma, according to a study of 1.7 million births.
The Norwegian Institute of Public Health research found that the risk of asthma was even higher in infants who had an emergency caesarean section.
Published in the Journal of Paediatrics, the study looked at babies born in Norway between 1967 and 1998 and followed the children until 2002 or until they were 18.
Study author Mette Tollanes said there were two theories to explain why caesarean born babies were more prone to asthma.
The first is that babies who are born by caesarean section are not exposed to their mothers bacteria during birth, which is detrimental for development of the immune system, she said.
The other is that babies born by caesarean section have more breathing problems after birth because they are less exposed to stress hormones and compression of the chest.
She said stress hormones helped babies empty their lungs of amniotic fluid and a lack of hormone exposure may affect long-term lung function.
Telethon Institute for Child Health Research paediatric respiratory physician Peter Sly said the study backed previous findings, including WA research, which had shown asthma risk was higher in caesarean babies.
Its solid data and if theres a message here, its heres yet another reason why women should not have elective caesareans, he said. Thirty per cent of Australian babies are born by caesarean and WA has the countrys highest rate at 33 per cent.
Professor Sly said a natural delivery switched on many immunological and hormonal triggers that helped babies prepare for life outside the womb.
Its almost like a switching mechanism that says, righto baby youve got to get out into the big wide world, you need this, this and this, and without that then a lot of these mechanisms dont kick in, he said.
He said caesarean birth alone was unlikely to cause asthma, with genetic predispositions working in combination with other risk factors.