Prenatal stress and risk of infectious diseases in offspring.

Animal studies have suggested that prenatal stress could affect the immune system of the offspring. In a nation-wide cohort of all Danish children born from 1977 to 2004, the authors examined the association between prenatal stress, defined as maternal exposure to a stressful life event during pregnancy or in the 3-year period before conception, and the risk of severe or less severe infectious disease hospitalization in childhood. Log-linear Poisson regression models provided estimates of rate ratios. Compared with nonexposed children, children exposed prenatally to stress had a 25% (rate ratio (RR) = 1.25, 95% confidence interval (CI): 1.06, 1.47) and a 31% (RR = 1.31, 95% CI: 1.27, 1.35) increased risk of being hospitalized with a severe or a less severe infectious disease, respectively. Children born to mothers exposed to a stressful life event during pregnancy, during the 11 months before, or during the 12-35 months before conception were at 71% (RR = 1.71, 95% CI: 1.20, 2.45), 42% (RR = 1.42, 95% CI: 1.13, 1.78), and no increased (RR = 0.86, 95% CI: 0.63, 1.18) risk of severe infectious disease hospitalization. No obvious association between risk of less severe infectious disease hospitalization and timing of maternal exposure was observed. Although the authors could not determine whether this is a biologic effect of prenatal stress or an effect of other factors related indirectly to a stressful life event, their results add new information about the consequences of prenatal stress.