Risk of miscarriage among users of corticosteroid hormones: a population-based nested case-control study

BACKGROUND The purpose of this nested case-control study in Denmark was to study the association between use of corticosteroids and risk of miscarriage. METHODS We identified prescriptions for corticosteroids before the miscarriage/index date. We estimated odds ratios (ORs) for miscarriage and for early (<13 weeks) and late (13-21 weeks) miscarriage adjusting for age, history of diabetes and epilepsy, and nonsteroidal anti-inflammatory drug use. RESULTS We identified 10,974 women with miscarriage and 109,740 controls. Prevalence of inhaled corticosteroid use within 60 days before the index date was 1.3% among the cases and 1.0% among the controls (OR = 1.20; 95% confidence interval [CI] 1.01-1.44). Prevalence of oral corticosteroid use within 60 days before the index date was 0.3% for both cases and controls (OR = 0.78; 95% CI 0.53-1.15). For inhaled and oral corticosteroids, the ORs of early miscarriage were 1.22 (95% CI 1.01-1.49) and 0.81 (95% CI 0.55-1.20), respectively. CONCLUSION Use of inhaled corticosteroids was associated with a slightly increased risk of early miscarriage, but explanations alternative to causal ones were possible.