Assisted hatching involves the use of mechanical or chemical thinning of the zona pellucida (outer shell) of the fertilized egg, prior to transfer (Figure 10).
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.
The embryos of women with endometriosis and poor quality (fragmented) embryos may also have this problem. The technique of assisted hatching was introduced to enhance the embryos ability to hatch, and thus implant, after transfer.