BACKGROUND: Recent evidence suggests that prenatal maternal distress increases the risk of allergic diseases in offspring. However, the effect of prenatal maternal depression and anxiety on atopic dermatitis (AD) risk remains poorly understood. OBJECTIVE: We investigated whether prenatal maternal distress is associated with AD risk in offspring and whether the mechanism is mediated by reactive oxygen species. METHODS: Two general population-based birth cohorts formed the study. One cohort (Cohort for Childhood Origin of Asthma and Allergic Diseases [COCOA]) consisted of 973 mother-baby dyads, and the other (Panel Study on Korean Children [PSKC]) consisted of 1531 mother-baby dyads. The association between prenatal distress and AD was assessed by using Cox proportional hazards and logistic regression models. In COCOA placental 11beta-hydroxysteroid dehydrogenase type 2 and glutathione levels and serum IgE levels in 1-year-old children were measured. RESULTS: In COCOA and PSKC AD occurred in 30.6% (lifetime prevalence) and 11.6% (1 year prevalence) of offspring, respectively. Prenatal maternal distress increased the risk of AD in offspring, both in COCOA (hazard ratio for depression, 1.31 [95% CI, 1.02-1.69]: hazard ratio for anxiety, 1.41 [95% CI, 1.06-1.89]) and PSKC (odds ratio for distress, 1.85 [95% CI, 1.06-3.25]). In COCOA both prenatal maternal depression and anxiety scores were positively related to the predicted probability of AD (P < .001 in both). Prenatal distress decreased placental glutathione to glutathione disulfide ratios (P = .037) and, especially in those who later had AD, decreased placental 11beta-hydroxysteroid dehydrogenase type 2 levels (P = .010) and increased IgE levels at 1 year of age (P = .005). CONCLUSION: Prenatal maternal depression and anxiety promote risk of AD in offspring. Maternal distress increases the predicted probability of AD. The mechanism might involve chronic stress, abnormal steroid levels, and reactive oxygen species.