Abstract
By using DNA cytofluorometry, DNA ploidy and the distribution pattern of human trophoblasts at different sites were studied throughout pregnancy, and the proliferative activity during cell differentiation of trophoblasts was discussed. In the first and second trimesters, cytofluorometric nuclear DNA analysis demonstrated that cytotrophoblasts in the tip of the anchoring villi (proximal portion of the cell column) consisted of proliferating diploid and tetraploid populations. Cytotrophoblasts in the distal portion of the cell columns consisted of non-proliferating diploid and tetraploid trophoblasts, as also did intermediate trophoblasts invading the maternal tissue. Villous trophoblasts consisted of proliferating diploid populations. In term placenta, villous trophoblasts were proliferating, diploid, whereas X-cells in the decidual tissue consisted of non-proliferating diploid and tetraploid populations. It was concluded that (1) trophoblasts in the generative zone consist of proliferating diploid and tetraploid populations, (2) intermediate trophoblasts having 4c DNA content were not proliferative, and (3) cytrotrophoblasts in the chorionic villi still had proliferative activity even in the term placenta.