Holly Horan is a doctoral candidate in the Applied Anthropology program and a recipient of the 2015-2016 Ryoichi Sasakawa Young Leaders Fellowship Fund (SYLFF). These funds will be directed towards Horan’s dissertation research, which focuses on the relationship between perceived, prenatal maternal stress, hair cortisol concentrations, and gestational age at delivery in Puerto Rico. Currently, Puerto Rico has the highest rate of preterm birth in the entire United States (U.S.) jurisdiction, and the most common epidemiological variables linked to preterm birth in other places do not explain this rate. Existing research is insufficient for assessing multiple measures of maternal stress on gestational outcomes within a single study; these relationships have also never been explored in the Puerto Rican context. Horan, in collaboration with Dr. Melissa Cheyney and Puerto Rican partners, plans to use a multi-phase, mixed-methods and ethnographic research design to: a) characterize the variable array of pregnancy-specific and non-specific stressors experienced by a diverse, voluntary sample of pregnant Puerto Rican women from the first trimester through the four to eight-week postpartum period; b) assess the degree to which study participants’ experiences of stress, as measured using two validated and locally-tailored stress assessment tools, predict hair cortisol concentration levels by each trimester and in the first four to eight weeks postpartum; and c) estimate the effects of perceived stress and hair cortisol concentrations on gestational age at delivery. This proposed research aims to address some of the methodological and contextual gaps in current prematurity research using a culturally-situated and integrated biocultural approach aimed at identifying and describing the potential role of subjective, perceived maternal stress and hair cortisol concentrations in preterm birth. This work will advance biocultural theories of local biologies and prematurity research specifically, and inform public health and clinical interventions focused on reducing early birth.