PROJECT SUMMARY / ABSTRACT This project is responding to the Notice “Ancillary reproductive health projects to existing large and/or longitudinal studies, as an Administrative Supplement to the parent grant R01 HD028016 ‘Metabolic Markers and Predictors of Childhood Obesity. This project is designed to assess the reproductive health in a large cohort of women in their 20’s, 30’s, and 40’s who previously underwent metabolic phenotyping as adolescents with obesity. The goal is to determine the characteristics of early obesity that play a role in future reproductive pathologies. The study strategy will generate subgroups with deepening biological measures to enable the breadth of research from epidemiology to the mechanism. First, we will study the cohort of women over 18 using a computer-generated review of their medical records to determine updated contact information and incidence of reproductive disorders (Subgroup 1). Then we will use this refined cohort to increase the depth of data by re-contacting and consenting 500 women to complete a questionnaire with details about their reproductive events and metabolic health (Subgroup 2). From these participants, we will invite 200 women for a research visit to measure anthropometrics and to donate fasting serum (Subgroup 3). Sub-group 3 will represent participants in the highest and lowest quartile of either hepatic and visceral fat per the MRI data obtained when they were adolescents or insulin area under the curve per their first oral glucose tolerance test. Finally, we will invite even a smaller subgroup of 20 women to donate a piece of endometrium via biopsy (Subgroup 4). Data and biospecimens will be protected and shared with investigators for hypothesis-driven research.