Asthma is chronic disease ofmultifactorial etiologic and exposure perinatal factors can determine the
development of airway inflammation. High prevalence of asthma in developing
countries accompanies the increase in the Cesarean Section (CS) rate in the
same period. Cesarean births in some countries of Latin America reach the
50% prevalence, in the Brazilian, public and private health services the rate
CS is considerate highest in the world. However, the association between
CS and asthma is still a controversial issue with conflicting data in the
literature due to potential confounding of several other determinants of asthma.
The mechanism to explain its
association between CS and asthma refers to the hygiene hypothesis. Decrease
exposure to certain types of microorganisms early in life would lead to
insufficient stimulation of T1 lymphocytes and consequences predominance of allergic
response of the type T2, responsible for the development of asthma and allergic
reactions. In children born CS the initial colonization of intestinal micro
flora is composed by bacteria from colonization of the skin and those related
to the hospital environment and these bacteria are capable of modulating the
type of immune response to the type T2.
The EPIC hypothesis (EpigeneticImpact of Childbirth) has also been proposed for explain the association
between CS and asthma; this suggests that the genome of fetus undergoes
remodelling in chromantin architecture and DNA methylation during the
intrapartum period and cause susceptibility to diseases. Children born CS have
higher DNA methylation than children born of vaginal delivery. The third
hypothesis to explain the association between CS and asthma is the lowest rate
of onset and duration of exclusive breastfeeding in children born cesarean, the
maternal milk would have a protective effect for asthma due to the
immunomodulators, low proportion of IL10 and more of IL13 and gamma interferon.
Studies that assessed the association between CS and asthma
presented different results. Association between asthma and CS was reported by
Roduit, et al. [10], in a prospective cohort study of 2.917 children, found a
significant association between delivery by CS and asthma OR = 1.77 CI 95%
(1.03-1.32) and the risk was increased in the presence of parental history of
atopy. Almqvist, et al. evaluated a retrospective cohort of 87,500
cesarean births and risk of asthma in children and adolescents CS was
associated with the use of asthma.
drugs OR: 1.13; 95% CI (1.04-1.24)
and diagnosis of asthma OR: 1.20 95% CI (1.05-1.37), adjusted by family history
of atopy, weight at birth, gestational age, gender, Apgar score and age
maternal. Tollanes, et al. found a high risk for asthma in children born
of emergency CS with OR: 1.42; CI 95 (1.12-1.62) and elective CS with OR 1.59;
95% CI (1.44-1.55) being the highest risk for asthma in preterm infants. Kero,
et al. evaluated records of 59,927 children and found association between
CS and asthma with OR: 1.21; CI 95% (1.08-1.36) and atopic asthma OR: 2.2; 95%
CI (1.06-4.64), adjusted for maternal age, gender and born. Salam et al. Evaluated a cohort of 3,464 children born ≥37 weeks of gestation and birth
weight ≥2,500 kg and a structured asthma questionnaire was applied. CS
represented risk factor for asthma OR: 1.33; CI 95% (1.01-1.75). Bager, et al. evaluated 9,722 women from a cohort in the Denmark for type of delivery,
gestational age, weight and height at birth, asthma and rhinitis obtained by
the local registry system and CS associated with asthma OR: 1.33;CI 95%
(1.2-1.74) but not allergic rhinitis OR: 1.16; 95% CI (0.90-1.49). Gessner and
Chimonas 23 evaluated 37,349 children aged 5-9 years of a retrospective birth
cohort. Asthma was confirmed by the Standard International Classification of
Diseases 9th Revision codes. Asthma was associated with preterm
birth but not with small for gestational age status. CS represented risk factor
for asthma or hospitalizations for asthma OR: 1.4; 95% CI (1.08-2.2).
In a prospective cohort study of 12,367 children Maitra, et al. Found no association between delivery by CS and asthma (OR= 1.14; 95% CI
0.9–1.4). Brandão, et al. evaluated 672 children with asthma and allergic
rhinitis found no association between CS and asthma however there was
association between CS and allergic rhinitis, adjusted for the main confounding
variables for asthma. Mallen, et al. using population-based registers
evaluated conditions of birth and asthma, allergic rhinitis, eczema and hay
fever in 567 adults. CS was not associated with asthma OR: 1.71; 95% CI
(0.76-6.84), rhinitis, eczema or hay fever. Vonk, et al. evaluated 597
adults using birth data on labour for delivery type and diagnosis for asthma
and atopy after 20-year follow-up, CS was not risk factor for asthma OR: 1.77;
95% CI (0.98-3.51). Bernsen, et al. evaluated 1,797 children in a cohort
through birth data records on type of birth and asthma, eczema and allergy at
six years of age. CS was not a risk for asthma OR: 1.03; 95% CI (0.51-2.08).
Nathan, et al. evaluated 156 children in a control case study at the age of
3-15 years. Seventy-eight children with diagnosis of asthma and seventy-eight
controls were evaluated for CS. There was no association between CS and asthma
OR: 1.21; 95% CI (0.6-2.41). Rusconi, et al. performed a cross-sectional
study in 15,609 children diagnosed with asthma less than five years old of age.
CS was associated with asthma and atopy. The association was of greater
magnitude in children of no atopic parent. The perinatal variables, gestational
age and low birth weight had low frequency in children of the CS.
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