ABSTRACT
The treatment of human infertility through the assisted reproductive techniques (ART) continues to be comparatively ineffi cient. Despite the common practice of multiple embryo transfers, all in vitro fertilization-embryo transfer (IVF-ET) procedures performed in the United States in 2006 resulted in a mean 35.4% delivery rate per embryo transfer (1). Although this IVF-ET delivery rate is actually an improvement over the preceding years, it is obvious that the majority of IVF-ET cycles still fail. While a clearly attributed 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 losses occur, the largest percentage of failed IVF-ET 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.
