Embryological strategies for overcoming recurrent assisted reproductive technology treatment failure.

In every assisted reproductive technology (ART) programme there are patients who experience repeated failure. If all laboratory and stimulation parameters are controlled, it is assumed that the underlying cause of failure is physiological, and is attributable to either of the gametes or the embryo. Within the laboratory, few tools are available, other than careful observation and embryo selection, to aid in selecting the right embryo to overcome this failure. The morphology of the zygote, the state of the cleaving embryos on day 2 and day 3 of development, and the blastocyst can influence implantation rates. However, without functional gametes it is unlikely that success can be achieved. An early indicator of this functionality is the morphology of the zygote, which can be influenced by either the oocyte or the spermatozoon, and can be altered by either improving oocyte quality during stimulation or by using donor sperm if the failure to conceive is attributable to the male gamete. Subsequently, selecting embryos for transfer on the basis of the morphology of zygotes and embryos at day 3 or day 5 of development with the addition of fragmentation scoring and assisted hatching has been found to overcome many cases of repetitive failure to conceive after ART.