Project Abstract Periodontitis is the most common chronic health condition in humans and affects an estimated 38% of adult women in the United States. Research has demonstrated a connection between periodontitis and other adverse health outcomes, including reproductive health outcomes of preeclampsia, low birthweight, and preterm birth. However, trials evaluating periodontal treatment in pregnancy have not found a consistent benefit for perinatal outcomes, suggesting that establishment of oral health prior to pregnancy may be required to influence birth outcomes. Thus, research into oral health in the preconception period may provide important insights into potential opportunities for oral health promotion, particularly because attempting conception is often accompanied with behavior changes. Prior research by this investigator evaluating preconception oral health found an association between self-reported preconception periodontitis and a prolonged time-to- pregnancy, but the association between preconception periodontitis and other perinatal outcomes remains uncharacterized. The aim of this research is to address this gap in the literature by providing insights into the causes and consequences of oral health in the preconception period using data from a large, prospective cohort study that follows women from the time they are planning a pregnancy (e.g., preconception). Specifically, Aim 1 will assess predictors of oral health and dental service use in the preconception period. Aim 2 will leverage a Target Trial Framework to emulate a randomized controlled trial to evaluate the impact of preconception receipt of periodontitis treatment among women with periodontitis on time-to-conception. Finally, Aim 3 will examine the association between preconception periodontitis and spontaneous abortion (commonly referred to as miscarriage). Taken together, the proposed project has the potential to provide broad insights into women’s oral health in the preconception period. An accompanying training plan dovetails with the research objectives to provide robust, hands-on training opportunities for the applicant to support her transition to an independent oral health epidemiologist with expertise in observational research methods. The training plan additionally outlines tailored mentorship opportunities from the sponsor and co-sponsors, all of whom are recognized experts in their fields with a track record of successful collaboration with each other and the applicant.