PROJECT SUMMARY The placenta plays crucial roles in ensuring adequate nourishment, protection, and support of the developing fetus, with important ramifications for long-term health. Once thought to be a perfect barrier between fetus and mother, the placenta is now understood to be involved in and perhaps to facilitate fetal-maternal communication through direct interaction and exchange of cells, extracellular vesicles, DNA and RNA. The quantity and type of placental material transferred to maternal circulation thus provides a window into the function of the placenta itself. The overarching goal of this proposal is to systematically evaluate the transcriptome and the epigenome of trophoblast cells and placental-derived extracellular vesicles in the maternal circulation during pregnancy, harnessing a novel, high-throughput approach for isolation of placental material. We will bring together an interdisciplinary team with expertise in bioengineering, obstetrics and reproductive sciences, genome sciences, and genomic biostatistics to study a meticulously defined cohort of women enrolled in the biorepository of the Global Alliance to Prevent Prematurity and Stillbirth (GAPPS). Additionally, women with preeclampsia, a major manifestation of placental dysfunction, will serve as a comparator population. From these subjects, we will evaluate characteristics of nucleic acids, extracellular vesicles, and trophoblast cells transferred from the fetus to the mother during pregnancy. Specifically, we will isolate circulating trophoblast cells (using ensemble-decision aliquot ranking, eDAR) and syncytiotrophoblast- derived extracellular vesicles (using temperature-responsive enrichment module, TREM) from maternal circulation during pregnancy. Transcriptomic and epigenomic analysis of placental-derived material will establish foundational information about placentomics during pregnancy and inform future studies.