 50% Increased Risk Of Asthma In Children born by Caesarean Section
Source: Science News Daily Date: 06/26/08
Babies born by Caesarean section have a 50 % increased risk of developing asthma compared to babies born naturally. Emergency Caesarean sections
increase
the risk even further. This is shown in a new study based on data from
1.7 million births registered at the Medical Birth Registry at the
Norwegian Institute of Public Health.
The
goal of the study was to investigate the possible link between being
born by Caesarean section and later development of asthma.
Summarised results from the study:
*
Compared to children born in the natural way (i.e. spontaneously and
vaginally), children born by Caesarean section had an approximately 50
% increased risk of developing asthma.
* Children born vaginally, but with assistance from vacuum or forceps, had a 20 % increased risk of asthma.
*
For children born between 1988 and 1998, planned Caesarean section was
associated with an approximately 40 % increased risk of asthma while
emergency Caesarean section was associated with a 60 % increased risk.
"We
found a moderately strong association between birth by Caesarean
section and asthma in childhood," says doctor and research fellow Mette
Christophersen Tollånes, who works for both the Norwegian Institute of
Public Health and the Department of Public Health and Primary Health
Care at the University of Bergen, Norway.
Why do Caesarean sections give an increased risk of asthma?
Tollånes explains that there are two main theories about why Caesarean sections could cause 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. 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, since
these mechanisms contribute to emptying the lungs of amniotic fluid.
Maybe this can negatively affect lung function in the long term.
The
fact that emergency Caesarean section apparently has a stronger effect
on the risk of asthma than planned Caesarean section cannot easily be
explained by any of these theories. It is possible that there are other
common causes that can induce the need for Caesarean section and the
development of asthma, says Tollånes.
Information from 1.7 million births
The
authors looked at over 1.7 million births reported to the Medical Birth
Registry at the Norwegian Institute of Public Health in the period
1967-1998. Multiple births and children with congenital malformations
were excluded. The children were monitored until they became 18 years
old or through 2002.
The
study compared the proportions of children who received a basic -and/or
attendance benefit for asthma from the Social Security office after
spontaneous vaginal birth, assisted vaginal birth (forceps or vacuum),
and Caesarean section (planned Caesarean section and emergency
Caesarean section separate from and including 1988), respectively. 4
out of 1,000 children received benefits for asthma.
Journal reference:
1. Tollanes et al. Cesarean Section and Risk of Severe Childhood
Asthma: A Population-Based Cohort Study. The Journal of Pediatrics,
2008; DOI: 10.1016/j.jpeds.2008.01.029
Adapted from materials provided by Norwegian Institute of Public Health.
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