A national Japanese cohort finds no evidence that cesarean delivery increases the risks of eczema, wheezing, asthma or atopic dermatitis in early life, challenging concerns that the mode of birth alone leads to infant allergic disease.
Study: Association of caesarean section with asthma and atopic dermatitis in infants from the Japan Child and Environment Study. Image credit: Roman Fenton / Shutterstock
In a recent study published in the journal Scientific Reportsresearchers in Japan investigated associations between cesarean delivery and the development of eczema, wheezing, asthma, and atopic dermatitis in Japanese infants.
Increasing the Allergy Burden in Children’s Health
The incidence of allergic diseases has recently increased worldwide. In Japan, allergic diseases are a major health concern, with high rates of atopic dermatitis, wheezing and asthma seen in children. Meanwhile, caesarean section rates have also increased worldwide. Children born by caesarean section have an altered cytokine profile and gut flora compared to those born vaginally, although the clinical significance of these differences remains debatable.
Mode of delivery as a determinant of immune development
Therefore, the mode of delivery may be a critical factor influencing the development of the immune system and the incidence of disease in infants. The relationship between cesarean section and allergic diseases remains controversial, with some studies suggesting associations between allergic diseases and cesarean section, while others report no associations.
Cohort and JECS study population characteristics
In the present study, researchers investigated associations between cesarean delivery and the development of eczema and wheezing among Japanese infants. The team used data from the Japan Environment and Children Study (JECS), a large cohort study examining the impact of environmental factors on children’s health. THE JECS included 103,062 pregnancies between January 2011 and March 2014.
Methods of data collection and evaluation of results
The current study used his March 2018 data set JECS and those with miscarriage, multiple babies or stillbirth are excluded. Self-reported questionnaires were administered to collect information about pregnancy and children. Atopic dermatitis, wheezing, asthma and eczema were assessed based on information provided when the children were one year old. Participants were assigned to vaginal or caesarean section based on mode of delivery.
Classification of Emergency and Elective Cesarean Section
The caesarean section group was further divided into an elective or emergency delivery group. Emergency caesarean section included non-reassuring fetal condition, gestational hypertension syndrome, premature rupture of membranes, cephalopelvic disproportion, endometrial infection, obstructed or delayed delivery, and other complications.
Elective caesarean section included fetal malpresentation, placenta previa, repeat caesarean section, and history of uterine surgery. The researchers used multiple logistic regression analyses, adjusted for potential confounders, to assess the risks of eczema, atopic dermatitis, asthma, and wheezing associated with cesarean delivery. Odds ratios and 95% confidence intervals were calculated.
Confounding Adjustment and Statistical Analysis Approach
Confounding factors included sex, parity, maternal age at pregnancy, gestational age (GA), maternal allergy history, smoking status, maternal passive smoking during pregnancy, pet ownership, marital status, small for GA (SGA), mother’s level of education, annual family income, breastfeeding at six months and infant exposure to secondhand smoke. Finally, the team assessed the associations between emergency and elective caesarean sections and the risks of eczema, asthma, atopic dermatitis and wheezing.
Distribution of delivery modes and allergy results
The study involved 74,639 mothers from JECS. Of these, 81.6% underwent vaginal delivery and 18.4% underwent caesarean section. Among cesarean deliveries, 41.4% were emergency and 58.6% were elective deliveries. In infants born by cesarean section, the rates of atopic dermatitis, asthma, eczema, and wheezing were 4.2%, 2.7%, 18.1%, and 20.2%, respectively.
The corresponding percentages in those born with vaginal delivery were 4.4%, 2.5%, 19% and 19.5% respectively. GA less than 39 weeks, parity of two or more, SGAmaternal age at pregnancy of 30 years or older, maternal smoking during pregnancy, higher maternal education, higher annual family income, and pet ownership were associated with an increased incidence of cesarean delivery. In contrast, breastfeeding at six months and primipara were associated with a reduced incidence of cesarean delivery.
Regression findings for allergies and respiratory outcomes
Adjusted regression analyzes revealed that cesarean delivery was not associated with a higher risk of infant wheezing, asthma, atopic dermatitis, or eczema. All adjusted odds ratios had 95% confidence intervals that included 1.0. Similarly, elective delivery was not associated with an increased risk of eczema, wheezing, atopic dermatitis or asthma. However, emergency delivery was associated with reduced odds of eczema (adjusted odds ratio 0.91, 95% confidence interval 0.85 to 0.98), representing a modest risk reduction of 9%.
Interpretation of findings and diagnostic limitations
Overall, cesarean delivery was not associated with the development of eczema or wheezing in infants up to 1 year of age. Similarly, emergency and elective cesarean deliveries did not increase the odds of eczema and wheezing.
The study treated eczema, defined as a recurrent pruritic rash, and atopic dermatitis, defined as a clinician-diagnosed condition, as separate outcomes, a distinction relevant for clinical interpretation.
Limitations of the study include the use of self-reported data, which may have led to underreporting, a narrow window of outcome definition in the first year of life, which may be too early to observe associations, particularly for asthma, which is difficult to reliably diagnose in infants, lack of disease severity data, and potential unmeasured misinformation among potential confounders and confounders.
The authors define these null findings as strong evidence against a significant association between cesarean delivery and the development of early allergic disease.
