Interfering with implantation by postcoital estrogen administration. II. Endometrium epithelial cell ultrastructure.

Secretory human endometrium was studied by electron microscopy after high-dose ethinylestradiol administration, a method used for interception (morning-after pill). Medicated (experimental) cycles were compared to non-medicated (control) cycles in the same volunteers. The nucleolar channel system typically present in the nucleus of the epithelial cell in secretory phase of the human endometrium disappears completely as a result of this treatment, resulting in a nucleolar basket structure. Glycogen deposits were prominent at the basal membrane and in the apex of the cell during the experimental cycle. Giant mitochondria were observed to occur to similar extent during control and treatment cycles. This study confirms the morphological delay found in light microscopic studies, published earlier with diethylstilbestrol and with ethinylestradiol.