The human placenta development and anatomy

The human placenta is a specialized fetomaternal organ whose architecture evolves throughout pregnancy. Its development begins with implantation, followed by the differentiation of trophoblast lineages that establish the early villous structures and mediate subsequent exchange between the maternal and fetal circulations. By the end of the second trimester, coordinated remodeling of villous stroma, vasculature, and syncytium transforms the placenta into a highly specialized interface capable of meeting the growing demands of pregnancy. Despite extensive research in this area, most developmental accounts emphasize early morphogenesis, leaving the structural transitions of mid- and late gestation underexplored These later phases are critical for understanding how architectural specialization supports placental function and how deviations in these processes underpin pregnancy complications. This review synthesizes current understanding of placental morphogenesis and histomorphology across gestation. It integrates classical placental histology findings with recent advances in three-dimensional imaging, lineage tracing, and vascular modeling. By combining developmental and structural perspectives, this review offers an updated understanding of how the architecture of the placenta evolves to sustain pregnancy.