Recently, chronic stress has drawn great attention as an underlying mechanism of preterm birth (PTB) among racial/ethnic minority women. However, the association between chronic stress and PTB is not clearly understood. In fact, existing chronic stress models do not agree on definitions and assessments of chronic stress, rarely reflect racial/ethnic differences in chronic stress experiences, and overlook the cumulative nature of chronic stress over time. The purpose of this dissertation was to determine if chronic stress before and during pregnancy explains the maternal age-graded PTB risk among four racial/ethnic groups of women (non-Hispanic [N-H] Whites, N-H Blacks, Hispanics, and Asians) in the U.S. Paper 1 is a systematic literature review that identified chronic stressors affecting adverse birth outcomes among the four racial/ethnic groups. Building on findings from Paper 1, Paper 2 examined factor structures of chronic stress unique to the four racial/ethnic groups through exploratory factor analysis. From this analysis, a race/ethnicity-specific composite index of chronic stress was developed as an operational definition of chronic stress for Paper 3. Paper 3 then investigated the moderating effect of maternal age on the chronic stress-PTB relationship stratified by race/ethnicity through logistic regression. Papers 2 and 3 implemented secondary analysis of the Pregnancy Risk Assessment Monitoring System for Washington State and New York City (2004-2007). Paper 1 found that the extant chronic stress measures tended to be unstandardized, incomprehensive, independent, or universal across race/ethnicity, weakening the accuracy of appraised chronic stress for women in each racial/ethnic group. Paper 2 noted that the four racial/ethnic groups analyzed shared financial hardship, perceived isolation, and physical violence as significant sources of chronic stress, despite intergroup variations particularly in their physical violence experience. Paper 3 observed a maternal age-related increase in PTB (i.e., weathering) among all racial/ethnic groups (except for Asians) with high chronic stress in unadjusted and adjusted models. Experience of race bias exacerbated weathering among racial/ethnic minority women with high chronic stress. This study will contribute to narrowing the racial/ethnic gaps in PTB through elucidating heterogeneity of the chronic stress mechanism among racial/ethnic groups and developing theory-driven, race/ethnicity-specific interventions to prevent exposure to chronic stressors and foster women’s resilience over the life course.