Abstract
Biopsies were obtained from 4 women on cycle days 10–12 and 20–23 before the insertion of a copper-T device and on the same stages several times during one year with the device in place. Further control biopsies were obtained on the same cycle days from 3 women having a Tatum-T device without copper. The biopsies were processed for light and electron microscopy of both glandular and luminal uterine epithelium. The copper-influenced endometria differed from the controls by lacking light areas in the cytoplasm. The light areas are associated with carbohydrate metabolism and their lacking might indicate an impaired degradation of glycogen. Thus, the secretory activity of the epithelium can be faulty resulting in an interference in the viability of the blastocyst.