Assisted hatching involves the use of mechanical or chemical thinning of the zona pellucida (outer shell) of the fertilized egg, prior to transfer.
It is believed this outer shell becomes thicker and hardened with aging of the oocyte. As such, women of advanced age or with an elevated FSH level on day 3 (“ovarian age”) may have decreased chance for embryo implantation.
During these initial stages of development, the embryo is contained in a layer of proteins known as the zona pellicuda (the shell of the egg). In order to successfully implant into the uterus, an embryo has to hatch out of the zona pellucida and attach to the uterine lining. The embryos of women with endometriosis, women of advanced age and women with poor quality (fragmented) embryos may also have implantation problems due to changes in the shell of the egg. The technique of assisted hatching was introduced to enhance the embryos ability to hatch, and thus implant, after transfer. Assisted hatching is most commonly performed using a LASER.