Use of corticosteroids during pregnancy and risk of asthma in offspring: a nationwide Danish cohort study

OBJECTIVE: To examine whether in utero exposure to local and systemic corticosteroids is associated with asthma development in offspring. DESIGN: Cohort study. SETTING: Denmark. PARTICIPANTS: We included all singletons born alive in Denmark between 1996 and 2009. Data on maternal corticosteroid use, asthma in offspring and covariates were obtained from medical registries. MAIN OUTCOME MEASURES: We compared asthma risks of children prenatally exposed to corticosteroids and of children of former corticosteroid users with that of unexposed children. We computed absolute risks and used proportional-hazards regression to compute adjusted HRs (aHRs). Using logistic regression we compared exposed children with unexposed siblings in a ‘within-mother-between-pregnancy’ analysis. Adjustment addressed varying length of follow-up. RESULTS: We identified 877 778 children, 3.6% of whom were prenatally exposed to systemic (n=5327) or local (n=24 436) corticosteroids. A total of 105 677 children developed asthma during follow-up with a 10-year risk of 18.4% among the exposed and 13.5% among the unexposed. The aHR was 1.54 (95% CI 1.45 to 1.65) for systemic use, 1.45 (95% CI 1.40 to 1.50) for local use and 1.32 (95% CI 1.30 to 1.34) for former use. The adjusted OR of the ‘within-mother-between-pregnancy’ analysis was 1.11 (95% CI 0.98 to 1.25). CONCLUSIONS: These population-based data do not support a strong causal association between maternal corticosteroid use during pregnancy and increased asthma risk in offspring.