Recurrent implantation failure (RIF) is an undefined, quite often, clinical phenomenon that can result from the repeated failure of embryo transfers to obtain a viable pregnancy. Careful clinical evaluation prior to assisted reproduction can uncover various treatable causes, including endocrine dysfunction, fibroid(s), polyp(s), adhesions, uterine malformations. Despite the fact that it is often encountered and has a critical role in Assisted Reproductive Technique (ART) and human reproduction, RIF's do not yet have an agreed-on definition, and its etiologic factors have not been entirely determined. ART is a complex treatment with a variable percentage of success among patients and care providers. ART depends on several factors that are not always known and probably not always the same. When confronted with repeated ART failure, medical care providers should try to determine whether the cause is an embryo or endometrium related. One of the most common causes of pregnancy failure is aneuploidy. Therefore, it is likely that this represents a common cause of RIF. Other RIF potential causes include immune and endometrial factors; however, with a very poorly defined role. Recent data indicate that the possible endometrial causes of RIF are very rare, thereby throwing into doubt all endometrial receptivity assays. All recent reports indicate that the true origin of RIF is probably due to the "egg".
Keywords: Assisted Reproductive Technique; euploid embryo transfer; frozen embryo transfer; reccurent implantation failure.