[Electron microscope study of the surface of human placental villi at the onset and at the end of gestation].

The surface of the syncytiotrophoblast covering the human placental villi at the first month and at the end of pregnancy has been observed using both Scanning and Tranmission electron microscopy. The ultrastructural changes have been compared and related to the physiological activity of the trophoblast during the maturation of the placenta.