Comparison of endometrial biopsies of fertile women and women with repeated implantation failure at the ultrastructural level.

Background/aim: The aim of this study was to compare the cellular properties of endometrial tissues from fertile patients and patients having at least 3 previous in vitro fertilization failures, during the implantation window. The ultrastructural evaluation of the endometrium in the implantation window may shed light on the complexity of the implantation failure paradigm. Materials and methods: The study involved 23 women, 14 infertile with a clinical diagnosis of repeated implantation failure (RIF) and 9 fertile, defined as the control group. Endometrial samples were examined by transmission electron microscopy (TEM). Results: In the control group, secretory vacuoles and cytoplasmic projections filled with secretory material, called pinopodes, were noted; microvilli were observed on some apical surfaces; and ciliated cells were absent. In the RIF group, the number of pinopodes was remarkably lower, with some of them being immature. Moreover, decidualization of stromal cells was not frequent and fewer epithelial cells with poor secretory vacuoles were discerned. Conclusion: TEM analyses of endometrial samples from the RIF group revealed dramatic differences at the ultrastructural level compared to the controls, which may well be an underlying cause of their infertility.