Summary/Abstract Young adulthood is the life stage when we should achieve peak health. Physically, young adults will have completed their growth, reached maximal lean body mass, and have optimal fertility. Many young adults will have completed school and live independently. While few young adults have overt chronic disease, many already have substantial risk factors such as hypertension, hyperglycemia, and obesity. Moreover, suboptimal lifestyle behaviors such as poor diet, insufficient sleep, and substance use, and symptoms of depression and anxiety prevent many young adults from reaching their full potential. Existing evidence suggests that the prenatal environment influences health and disease risks across the lifecourse. However, most human evidence is based on either short-term follow-up into childhood, when health is more plastic; or on retrospective data from adult cohorts in which exposures are limited or subject to substantial recall bias, and selection bias is likely considerable yet unquantifiable. The proposed project will address this topic leveraging the rich data already collected in the Project Viva pre- birth cohort. The project will include already-collected measures of prenatal maternal behaviors (diet, smoking, physical activity) and biology (inflammation, blood pressure, glycemia, weight gain, depressive/anxiety symptoms), as well as elements of the chemical (exposures to metals, PFAS, air pollution) and social environments (material hardship, neighborhood deprivation). Specific Aims will focus on following key domains of health to be assessed in 1000 young adults followed since prenatal life: Aim 1: Cardiometabolic Health, based on weight, waist circumference, blood pressure, and biomarkers (lipids, glycemia, inflammation). Aim 2: Reproductive Health, based on fertility markers including hormone levels, menstrual cycle characteristics (for women), and sperm quality/quantity (for men). Aim 3: Experiential Health and Wellbeing, based on perceived overall health and quality of life, measures of positive psychology (e.g. optimism), and low levels of depressive/anxiety symptoms Secondary Aim 4: Health behaviors, including diet and eating behaviors, physical and sedentary activities, tobacco and other substance use, and sleep. The primary hypothesis is that a more beneficial prenatal environment will be associated with better cardiometabolic, reproductive, and experiential health in young adulthood. Project Viva is uniquely positioned to address these important scientific questions. Ongoing support of this unique resource will provide an unparalleled opportunity to rigorously evaluate the extent to which developmental exposures influence health into adulthood.

Narrative The proposed project will examine the extent to which prenatal experiences predict health and disease risk in young adulthood. As health status tracks from young adulthood into later life and predicts future health and longevity, it is critical to better characterize the determinants of health in this life stage. The extent to which such exposures may have persistent health effects not only for the offspring themselves but for their reproductive health and future children is an important and highly innovative research opportunity.