Cesarean delivery may increase kids' asthma risk
Last Updated: 2008-07-03 14:38:46 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Babies born by Cesarean section may have a
moderately increased risk of developing asthma compared with those
born naturally, Norwegian researchers re****t after investigating this
link in a population-wide study.
Dr. Mette C. Tollanes, of the University of Bergen, in Norway, and
colleagues looked at the modes of delivery among more than 1.7 million
single births re****ted to the Medical Birth Registry of Norway between
1967 and 1998. They used registry data from Norway's National
Insurance Scheme to determine the number of children who, through the
age of 18 or the year 2002, developed severe asthma.
Between 1967 and 1998, asthma risk was about 50 percent higher among
children born by C-section compared with children born spontaneously
and vaginally, the researchers re****t. They found 19 percent increased
risk among children born by vaginal delivery requiring the use of
instruments (forceps or vacuum).
=46rom 1988 through 1998, when the birth registry designated between
emergency and planned C-section deliveries, unexpected differences
emerged. Compared with spontaneous vaginal deliveries during this
period, emergency C-sections carried higher asthma risk (59 percent)
than planned C-sections (42 percent increased risk). Instrument-
assisted vaginal deliveries brought a 14 percent increased asthma risk
during this 10-year period.
Overall, these findings confirm a moderate association between C-
section delivery and later development of asthma, Tollanes and
colleagues say. However, the reasons behind this association must
still be determined.
According to Tollanes, there are two main theories about why C-
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,"
Tollanes explains in a written statement.
"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," Tollanes said.
"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," Tollanes admits. "It is
possible that there are other common causes that can induce the need
for Caesarean section and the development of asthma."
SOURCE: The Journal of Pediatrics, June 2008
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