PROJECT SUMMARY The effect of early environmental exposures on child health and development is an important area of public health that no single cohort, or even a few, can answer alone – particularly when coupled with social determinants of health (SDOH) that may influence these exposures and modify their effects. Determining this effect becomes more challenging when considering that these exposures influence multiple interrelated health outcomes such as obesity, neurodevelopment and reproductive development. The ECHO-PROTECT Cohort Site in Puerto Rico (PR) will focus on these health outcomes, taking advantage of the rich and large sample size, diversity, and longitudinal nature of the national ECHO Cohort and multi-disciplinary expertise across the ECHO consortium. ECHO-PROTECT will contribute innovative research to (Aim 1) examine the influence of SDOH on maternal diet and obesity during pregnancy, child diet and obesity during early to middle childhood, and the relationship between maternal-child diet and onset of puberty and (Aim 2) determine the relationship between in utero and early childhood exposure to environmental chemicals, individually and as mixtures, and neurodevelopment and reproductive development, across early childhood, middle childhood, and adolescence. Most importantly, ECHO-PROTECT will build upon the ongoing ECHO-PROTECT cohort in PR (Aim 3) to follow up and collect data and biospecimens from the 1,100 children that are participating in the current ECHO- PROTECT cohort, as well as recruit an additional 1,200 pregnant participants, yielding 1,000 more children, for a total of 2,100 children contributing data and biospecimens to the ECHO Cohort from Puerto Rico – an underserved, highly-exposed population. The proposed 1,200 new pregnancies will include at least 125 completed pregnancies with preconception data (Aim 4), tracked from a cohort of 500 potential preconception participants and, if available, their conceiving partner. ECHO-PROTECT research will contribute meaningfully to ECHO’s mission, offering (a) an important cohort that will enrich consortium wide data, (b) significant, innovative science on the influence of SDOH and exposure to multiple chemicals on multiple interrelated health outcomes such as obesity, neurodevelopment, and reproductive development, and (c) expertise to lead and participate in additional new scientific directions involving biomarkers of exposure or biologic response, child brain or reproductive development, and statistical methods in collaboration with the ECHO consortium, to answer impactful and cutting-edge research questions. Results from our study will inform future clinical intervention, risk assessment and policy-setting efforts, with direct relevance to both the underserved population of Puerto Rico and the U.S. general population.