SRP199367 PRJNA544522 GSE131696 Sexually dimorphic crosstalk at the maternal-fetal interface The first trimester is a critical window of maternal-fetal communication for pregnancy. Using single cell RNA-sequencing to dissect placenta heterogeneity, we identified five major cell types (trophoblasts, stromal cells, hofbauer cells, antigen presenting cells and endothelial cells). We identified seven unique trophoblast subclusters, including new subtypes that transition into the terminal cell types, extra-villous trophoblasts and syncytiotrophoblasts. As fetal sex impacts pregnancy, we analyzed sex differences in each cell type and identified differences in immune cell function. TGFß1, ß-estradiol, and dihydrotestosterone emerge as upstream regulators of sexually dimorphic genes in a cell type specific manner. Thus, the fetal contribution at the maternal-fetal interface is cell and sex specific. Overall design: Examination of transcriptomic profiles at the single cell level in the primary tissues from first trimester human placenta. In total, 6 placental tissues were utilized, of which 3 were from female conceptions and 3 were from male conceptions. GSE131696 pubmed 32772088 parent_bioproject PRJNA545158