Syncytiotrophoblastic vesicles in placental intervillous space

Objective This study was undertaken to investigate the origin and function of vesicles found in the intervillous space. Study design A retrospective study was performed by using placental sections of different gestational ages. The number of vesicles was counted in each section of gestational age groups. Immunohistochemical staining for beta-human chorionic gonadotropin (beta-hCG) and human placental lactogen (hPL) was conducted to confirm the origin of vesicles. Results Staining for beta-hCG and hPL was prominent in vesicles separating from syncytiotrophoblast into the intervillous space. The numbers of vesicles were not significantly different in gestational age groups of 42 to 30 weeks and all vesicles disappeared in 9- to 5-week groups. Large vesicles tended to show degeneration and disintegration in the intervillous space. Conclusion The vesicles containing beta-hCG and hPL suggest a different secretory mechanism of syncytiotrophoblast.