Are there indications for "assisted hatching"?

Assisted hatching was first described in 1990. The introduction of an artif icial opening in the zona pellucida of the developing embryo should guarant ee successful hatching of the embryo at the blastocyst stage. Embryo hatchi ng is essential for subsequent implantation and for establishing a pregnanc y. The introduction of assisted hatching has initiated a controversial disc ussion about the significance of this technique. The development of new techniques, such as laser assisted hatching,and the increasing knowledge of the hatching process in vitro and in vivo has re-op ened this discussion. The farmer indications for assisted hatching,includin g maternal age (>38 years), a thick zona pellucida, and repeated failure of implantation despite the transfer of good embryos are still valid. Whether assisted hatching can raise the pregnancy rate following cryopreservation is questionable. Hatching in vivo is accomplished by embryonic and uterine factors. The detailed physiology of this process and possible disturbances have not yet been elucidated.