Harmful Effects of Hypothyroidism in Pregnancy Prompt New Guidelines
Posted Aug 08 2011 12:00am
News Author: Nancy A. Melville
CME Author: Penny Murata, MD
Breast-feeding appears to be linked with a
decreased risk for childhood asthma-related symptoms, according to
Fredriksson and colleagues in the November 28, 2007, issue of BMC Pediatrics.
However, the influence of a family history of asthma or allergy is not
clear. The link between breast-feeding and the risk for asthma might be
mediated by atopy or infection.
The current study by Sonnenschein-van der Voort and colleagues,
embedded in the population-based prospective cohort Generation R study,
described by Jaddoe and colleagues in the November 2010 issue of the European Journal of Epidemiology,
assesses the association of duration and exclusiveness of
breast-feeding with the risk for asthma-related symptoms in the first 4
years of life and whether the association is mediated by atopic or
Study Synopsis and Perspective
Preschool children who were not breast-fed or not
exclusively breast-fed for 6 months show increased rates of
asthma-related symptoms, such as wheezing, shortness of breath, and dry
cough, according to a study published online July 20 in the European Respiratory Journal.
Asthma symptoms in children, known to be a leading cause of
morbidity, have been linked in previous studies with lower rates of
breast-feeding, but the study from researchers in the Netherlands is
said to be the first to demonstrate an association between the length of
time a child was breast-fed and the number of wheezing episodes the
For the study, the researchers evaluated data on 5368 children that
was part of the Generation R study, a population-based prospective
cohort study of pregnant women and their children from fetal life on in
Rotterdam, the Netherlands.
They gathered information on breast-feeding duration, exclusiveness,
and asthma-related symptoms, including wheezing, shortness of breath,
dry cough, and persistent phlegm.
The results showed that, compared with children who were breast-fed
for at least 6 months, those who were never breast-fed were 1.4 and 1.5
times more likely to develop symptoms of wheezing and persistent phlegm,
In addition, children who were not exclusively breast-fed during the
first 4 months of life and were also fed milk or solids during that
period also were at higher risks of wheezing, shortness of breath, dry
cough, and persistent phlegm in their first 4 years vs those who were
exclusively breast-fed in their first 4 months.
Further adjusted analyses indicated that the associations of
breast-feeding with asthma-related symptoms were not explained by eczema
but, instead, were partly related to lower respiratory tract
Breast-feeding is widely believed to help reduce the risk for asthma
in younger children through a mediating effect on atopy and/or
infections, the study authors believe.
"Underlying mechanisms might include IgA [immunoglobulin A],
cytokines, especially TGF [transforming growth factor]-beta1, and
long-chain fatty acids in breast milk that stimulate the infant's immune
system," they explained.
"Also, glycans help the innate immune system to inhibit pathogen
binding to the host cell target ligand, and changes in the delicate
balance between pro- and anti-inflammatory compounds."
The protective effect of breast-feeding, in particular, appears to be
related to gut microflora that is changed with breast-feeding, they
"The gut microflora is suggested to be different between breastfed
and formula fed infants. Compared to breastfed infants, those who
receive formula feeding have a more complex microflora with more
facultative anaerobes, bacteroides and clostridia at higher levels and
frequencies," the study authors write.
"We speculate that this might decrease with increasing exclusivity of
breastfeeding, leading to lower infection risk and less wheezing by
influencing the development of the immune system. Due to this putative
effect on the development of the immune system, infections and
asthma-related symptoms might occur less frequent even years after
The results are in line with previous research showing up to a
2.22-fold increased risk of recurrent wheezing or asthma at the ages of 2
to 6 years among children who were not breast-fed or not exclusively
breast-fed until age 4 months.
These new findings add to the previous research by showing a
dose-response relationship between breast-feeding and the number of
wheezing episodes, said lead author Agnes Sonnenschein-van der Voort,
MSc, in a press release.
"The link of duration and exclusiveness of breastfeeding with
asthma-related symptoms during the first four years was independent of
infectious and atopic diseases," said Dr. Sonnenschein-van der Voort, a
researcher with the Erasmus Medical Center in the Netherlands.
"These results support current health policy strategies that promote
exclusive breastfeeding for 6 months in industrialized countries.
Further studies are needed to explore the protective effect of
breastfeeding on the various types of asthma in later life." Eur Respir J. Published online July 20, 2011.