trophoblast cell syncytiotrophoblast cell A cell from the outer syncytial layer of the trophoblast of an early mammalian embryo, directly associated with the maternal blood supply. It secretes hCG in order to maintain progesterone secretion and sustain a pregnancy. syncytial trophoblast cell https://github.com/obophenotype/cell-ontology/issues/2100 syncytiotrophoblastic cell FMA:83043 syntrophoblast cell plasmidotrophoblast cell