Hypothesis/Commentary Risk of Cancer among the Offspring of Women Who Experienced Parental Death during Pregnancy

The causal link between psychological stress and cancer, if any, remains unclear (1-4). It has been hypothesized that stressors, such as dramatic life events, might result in an impairment of the immune response, thus increasing the risk of malignancies (e.g., those associated with viral infections; refs. 1, 4). On the other hand, studies in monozygotic twins, in archived neonatal blood spots of patients, and in normal newborn cord bloods suggest that most pediatric leukemias are initiated in utero. Postnatal secondary genetic changes, usually triggered by abnormal immune responses to infections, seem to be additionally required for leukemia develop-ment (5-7). Although epidemiologic studies have been conducted to investigate the relationship between stress and cancer, their small size and the inadequate ascer