ABSTRACT
The treatment of human infertility through the assisted reproductive technologies continues to be comparatively inefficient. Despite the common practice of multiple embryo transfers, all in vitro fertilizationembryo transfer (IVF-ET) procedures performed in the United States in 1996 resulted in a mean 26.0% delivery rate per oocyte retrieval.1 Although this IVF-ET delivery rate is actually a slight improvement over the preceding years, it is obvious that the majority of IVF-ET cycles still fail. While a clearly attributable cause for cycle failure may occasionally be present, in most circumstances there is no apparent explanation other than failure of the implantation process. Although both subclinical and clinical pregnancy loss does occur, the largest percentage of failed IVFET cycles simply exhibit lack of implantation. In some patients, implantation failure occurs repeatedly. These latter patients continue to present unique challenges for the infertility specialist.
