The disparity between black and white infant mortality rates increased over the last decade, despite overall improvement in infant survival. Because most black infant deaths are related to preterm delivery, the discovery of the cause of premature birth in general and excess premature birth for black infants in particular is of paramount importance for reproductive health research. Substantial theoretic support exists for maternal stress as a risk factor for preterm birth. Traumatic events early in life may sensitize the adult to contemporary stresses and increase her vulnerability to stress-induced neuroendocrine or infection/inflammatory pathways to early parturition. In addition, an individual may prematurely age as a result of cumulative stress or a major traumatic event. This "stress age," which is synonymous with the concept of weathering and similar to the concept of allostatic load, may affect parturition through chronic conditions (such as hypertension) and in poorly understood pathophysiologic mechanisms that are related to increased chronologic age. One potential measure of stress age is maternal serum dehydroepiandrosterone sulfate. Maternal stress is a potential explanatory factor for excess preterm delivery among black women because of their exposure to racism-associated stress. However, few studies have addressed this question, and results are mixed. Future etiologic research must take into account the complexities of the measurement of stress age and past and current exposures to stress, which includes internalized racism and interpersonal racism.