[An ultrastructural dynamic study of trophoblast cells in human placenta]

Sixty-seven specimens of human placentae aged 5 to 41 weeks were collected and their trophoblastic cells studied dynamically under EM. Two kinds of cells, dark cytotrophoblasts and transitional syncytial trophoblasts were observed. Trophoblast fusion was also observed, and this phenomenon may have been related to the aggregation of syncytial cell nuclei and the formation of syncytial knots. During pregnancy, trophoblasts (especially syncytial trophoblasts) showed dynamic changes which were more prominent in the nuclei, including increased heterochromatin content and nuclear aggregation.