Abstract Both smoking and second hand smoke (SHS) exposure are established risk factors for chronic disease and cancer. While the prevalence of smoking has decreased in the population as whole, there are subgroups that are particularly vulnerable to smoke exposure, such as pregnant women and children, and it is recommended to eliminate exposure almost entirely among these subgroups. Many states are active in either planning or proposing new regulations limiting tobacco retail outlet (TRO) density as a means of reducing smoking. Presumably, reducing TRO density should lead to lower levels of adult smoking, which should also reduce maternal smoking during pregnancy and SHS exposure in children. There is scant evidence that TRO density is related to smoking behaviors, and there is no evidence showing that reducing TRO density will extend to vulnerable subgroups and those passively exposed, like pregnant women and children. The purpose of proposed study is to examine the extent to which TRO density is related to biomarkers of smoke exposure (cotinine) in 1000 women during their pregnancy and in 400 children aged 4-10 born of these mothers. In addition, the study will determine the degree to which cotinine levels and TRO density relate to health care utilization and costs during pregnancy and early childhood. To accomplish this study, the team will integrate data on biomarkers of smoke exposure and health-care utilization data from a longitudinal pre-birth cohort with publically available data sources on TROs and census data (American Community Survey). By better understanding the link that TROs have with smoke exposure and the related health-care costs associated with such exposure, we will be better positioned to make data-driven policies that aim to modify the TRO landscape. Successful completion of this project will provide evidence supporting continued efforts to expand policies reducing TRO density and retain them where they are being enacted.