Caesarean delivery associated with atopic dermatitis in young children

Key takeaways:

• Caesarean delivery had an adjusted hazard ratio of 1.12 for atopic dermatitis compared with vaginal delivery.
• Risks were higher with instrumental vaginal delivery and emergency and elected caesarean deliveries.

Children born by caesarean section had an increased risk for developing atopic dermatitis before age 5 years compared with children born by vaginal delivery, according to a study published in Pediatric Allergy and Immunology.

Associations between AD and instrumental vaginal delivery and emergency and elective caesarean delivery were found as well, Mwenya Mubanga, PhD, MPH, MS, MBChB, postdoctoral researcher, department of medical epidemiology and biostatistics, Karolinska Institutet, and colleagues wrote.

The register-based cohort study involved 1,399,406 singleton children (51.4% boys) born in Sweden between January 2006 and December 2018 (mean age at follow-up, 4.2 years; standard deviation (SD), 1.3). Mothers had a mean age of 30.4 years (SD, 5.2).

Specifically, 75.5% had an uncomplicated vaginal delivery, 6.8% had an instrumental vaginal delivery, 10% had an emergency caesarean section and 7.7% had an elective caesarean section. Also, 7.4% of the caesarean deliveries and 1.3% of the vaginal deliveries were at or before 34 full weeks of gestation.

With 6,029,542 person-years of follow-up, 17.4% of the population developed AD at a mean age of 2.72 years (SD, 1.8).

Models were based on age (model 1); age and sex (model 2); and multiple factors including age, sex, birthweight, gestational age, maternal age, parity, maternal history of asthma and maternal level of education (model 3). Analysis included sibling controls to account for familial confounders as well.

The researchers found associations between caesarean birth and higher risk for AD among children aged younger than 1 year with a hazard ratio of 1.11 (95% CI, 1.09-1.13) for model 1, a hazard ratio of 1.1 (95% CI, 1.08-1.12) for model 2 and an adjusted hazard ratio of 1.12 (95% CI, 1.1-1.14) for model 3.

Children aged 1 year and older with caesarean birth also had increased lower risk, although it was lower than the risks found for the younger group, with hazard ratios including 1.06 (95% CI, 1.04-1.07) for both model 1 and 2 and an adjusted hazard ratio of 1.05 (95% CI, 1.04-1.07) for model 3.

Among children aged younger than 1 year, in model 3, instrumental delivery had a higher risk for AD (aHR = 1.1; 95% CI, 1.07-1.13) than emergency (aHR = 1.12; 95% CI, 1.1-1.15) and elective (aHR = 1.13; 95% CI, 1.1-1.16) caesarean sections.

Adjusted hazard ratios for AD among children aged 1 year and older included 1.04 (95% CI, 1.02-1.06) for instrumental delivery, 1.05 (95% CI, 1.03-1.07) for emergency caesarean delivery and 1.06 (95% CI, 1.04-1.09) for elective caesarean delivery compared with vaginal delivery.

Caesarean delivery was associated with AD (aHR = 1.06; 95% CI, 1.01-1.11) compared with vaginal delivery among children aged younger than 1 year in the sibling analyses as well, but there was no elevated risk observed in children aged 1 year and older.

By subgroups, risks for AD in the sibling analysis were higher with instrumental delivery (aHR = 1.1; 95% CI, 1.05-1.16) and emergency caesarean delivery (adjusted HR = 1.11; 95% CI, 1.05-1.08) but not with elective caesarean delivery compared with uncomplicated vaginal delivery among children aged less than 1 year.

Further, in the sibling analysis, children aged 1 year and older did not see any increased risks for AD with instrumental vaginal delivery, emergency caesarean section or elective caesarean section compared with uncomplicated vaginal delivery. Overall, the researchers said, the sibling control analysis indicated some familial confounding.

Based on these findings, the researchers concluded that there was an association between caesarean birth and AD compared with vaginal delivery, in addition to associations between instrumental delivery and emergency and elective caesarean delivery, compared with uncomplicated vaginal delivery. Genetic and environmental factors confound these risks in children aged 1 to 5 years, the researchers continued, but not among younger children.

The researchers called for additional research to determine the mechanisms behind the risks seen in the different age groups since different periods of onset may indicate different subtypes of disease.