As a marker of chronic stress, allostatic load has been theoretically recognized as a potential contributor to racial disparities in birth outcomes. The purpose of this investigation was to identify associations between allostatic load and birth outcomes and to assess differences in allostatic load and its relation to birth outcomes between white and black women. Blood samples from 123 women at 26-28 weeks gestation were assayed for cholesterol, glycosylated hemoglobin, dehydroepiandrosterone-sulfate, and cortisol, with 42 women having complete data on all biomarkers and birth outcomes. Together with systolic blood pressure, these biomarkers were combined to create an allostatic load index. Multiple linear regression models were used to evaluate associations between allostatic load index and gestational age, birth weight, birth weight ratio, birth length, and head circumference. Black women had a significantly lower allostatic load index than white women (P < 0.05). Gestational age was the only outcome significantly associated with allostatic load in both unadjusted and adjusted models (P < 0.05). Gestational age decreased significantly with increasing allostatic load (adjusted β -0.18, 95 % CI -0.35, 0.00). A significant interaction with age indicated that the effect was less strong at higher maternal ages (adjusted interaction β 0.04, 95 % CI 0.00, 0.08). There was no racial difference in the effect of allostatic load on birth outcomes. These findings represent possible evidence of the effect of stress age on gestational age. As a measure of cumulative disadvantage, allostatic load may prove to be a contributor to the racial disparities in birth outcomes.