No Obvious Impact of Caesarean Delivery on Childhood Allergic Outcomes: Findings From Australian Cohorts

To assess associations between cesarean delivery and the development of childhood asthma, eczema, and impaired lung function.

The study included data from two contemporary population-based, longitudinal studies of allergic diseases in Australian children, HealthNuts (n = 3135) and Longitudinal Study of Australian Children (LSAC, n = 3654), at age 6–7 years old and lung function data from LSAC’s Child Health CheckPoint (n = 1502) at age 11–12 years old.

Parent-reported data on delivery mode at baseline and child’s current asthma and eczema were extracted from HealthNuts and LSAC between the ages of 6–7 years. Asthma was defined as a parental recall of physician diagnosis of asthma and asthma medication use or wheezing in the chest in the last 12 months. Eczema was defined as itchy rash coming and going for 6 months and located in at least one of the folds of elbows, behind knees, front of ankles, under buttocks or around neck, eyes, or ears. Logistic regression was used to estimate associations between delivery mode and asthma or eczema. Linear regression was used to examine lung function. Models were adjusted for potential confounding factors, including maternal age at birth, mother’s country of birth, maternal smoking during pregnancy, socioeconomic index, gestational age, and birth weight.

The proportion of infants born by cesarean delivery was similar across both studies. The prevalence of current parent-reported asthma was 12.9% in HealthNuts and 16.0% in LSAC. There was neither increased odds of eczema at age 6–7 years nor poorer measured lung function at age 11–12 based on mode of delivery in either of these general population-based cohorts. However, in the HealthNuts study, the odds of parent-reported asthma were about 25% higher in children 6–7 years old born by cesarean delivery than vaginal delivery (HealthNuts: aOR 1.25, 95% CI 1.00 to 1.57; LSAC: aOR 1.05, 95% CI 0.86 to 1.35). This association with cesarean delivery was similar for atopic and non-atopic asthma. In contrast, in LSAC, no association was evident between delivery mode and asthma. Associations were not modified by breastfeeding duration, maternal history of asthma/eczema, and factors related to microbial exposure like child care attendance, older siblings, and pet exposure.

This study found a small, inconsistent excess of childhood asthma, but not eczema or impaired lung function, in children born by cesarean delivery.

There has been recent interest in the potential link between the rising incidence of childhood allergic disease and the increased utilization of cesarean delivery. At this point, it is unclear whether this association results from alterations in the newborn microbiome from not passing through the birth canal, a lack of maternal stress hormones from scheduled cesarean sections, or some as yet unknown factor.