Screening of prospective parents to determine if their offspring are at risk for potentially devastating heritable conditions with genetic carrier screening has resulted in measurable decreases in the number of newborns affected by severe recessive disorders. Although professional societies such as the American College of Obstetricians and Gynecologists and the American College of Medical Genetics advocate for genetic carrier screening to be done prior to pregnancy (preconception), access to preconception genetic carrier screening remains low and inequitable. This is because implementation of carrier screening in a diverse national population is complicated and requires 1) understanding the barriers and facilitators of screening at all levels of healthcare delivery, 2) recognizing patient preferences for test delivery, and 3) clarifying potential personal health implications of carrier screening. This award will be used to address these three gaps in our understanding of preconception genetic carrier screening. First, I will interview key informants with experience at all levels of healthcare delivery about their perceptions of the barriers and facilitators to implementing preconception carrier screening programs. Second, I will systematically elicit patient preferences about how genetic carrier screening should be delivered using a discrete choice experiment. The discrete choice experiment will consist of a web-based survey in which different attributes of how preconception carrier screening is offered are varied and prospective patients must choose their preferred screening method. This survey will be administered to two separate cohorts of women of reproductive age to encourage a diversity of responses. Finally, I will use phenome-wide association study methods to investigate whether carriers of autosomal recessive disease are at high risk of other adult diseases. I will focus on CFTR, HBB, and GBA, which are implicated in the autosomal recessive disorders cystic fibrosis, sickle cell anemia, and Gaucher disease, respectively. This study will generate key pilot data that will be used to design testable implementation strategies to enable widespread use of preconception carrier screening. These strategies and their impact on patient care will subsequently be tested in a randomized clinical trial through a future grant application.