Cesarean births not linked to childhood asthma

The theory that whether a child born by cesarean section or in the normal way, via the birth canal, could affect his or her chances of developing asthma later in life, has been laid to rest.

According to new research the mode of delivery at birth appears to have no bearing on the subsequent development of asthma.

It is thought that the development of allergies and asthma may be influenced by the type of infections a child is exposed to very early in life, which in turn sets the immune system to respond normally or over-sensitively to allergens.

This 'hygiene hypothesis' contends that children who are overly protected against bacteria tend to develop allergies, because they need the exposure to develop a balanced immune system.

Lead researcher Dr. Young J. Juhn says that bacterial colonization of the gut in newborns delivered by cesarean section differs from that in newborns born by vaginal delivery, and this may influence the development of allergies.

Juhn and colleagues examined data on over 7000 children of whom 10 percent were delivered by cesarean section, in order to see if different bacterial exposure influenced the risk of asthma development or wheezing.

They found that over a 7 year period, the asthma occurred at a rate of 3.2 to 5.7 percent in the cesarean group and 2.6 to 6.7 percent in the vaginal delivery group.

These differences are not considered significant from a statistical standpoint.

Therefore the investigators concluded that either the hygiene hypothesis may be too simplistic or the influence of microbial organisms may be weaker than has been previously reported.

The research is published in the Journal of Allergy and Clinical Immunology, September 2005.