The outer covering of embryo is called Zona pellucida which is a cover protecting the integrity of the blastomeres inside. They should be dissolved or breached before the blastocyst gets attached with endometrial lining of uterus for proper nidation. When they are resistant for natural enzymes in the endometrial cavity which help in dissolving this, or when the women concerned is aged whose eggs may have harder & thicker zona, we may have to dissolve the zona partially before transferring them in to uterus. It helps in nidation at the earliest for better growth. The following are the methods used:
Out of these we follow the latest one called "Laser assisted hatching" system, which augments the success rates significantly by improving the implantation rates. This technique helps the blastocyst to hatch in time, by which the implantation potential is improved, where embryos have thicker zona pellucida and for cryopreserved Blastocyst/ Embroys too.
In Laser assisted hatching, a laser beam is used to thin the zone pellucida (outer shell) of the embryo before it is transferred into the uterus. This outer shell is believed to become thicker and hardened with aging of the oocytes (egg). Women of advanced age, or with an elevated follicle stimulating hormone (FSH) level on day three, may have decreased chance for embryo implantation. The embryos of women with endometriosis and poor quality embryos may also have this problem. The assisted hatching technique was introduced to enhance the embryos' ability to hatch, and thus implant, after uterine transfer.
You may be a candidate for assisted hatching if you are 38 years of age or older, have an elevated basal FSH level, or if you have previously had one or more IVF cycles in which your embryos failed to implant, despite otherwise good results. This could be used on cryopreserved embryos also to make better implantation potency.
It could be used on both DAY 3 / DAY 5 EMBRYOS. We use Laser Hatching Technology for the past 11 years on needy couples, which really boost the implantation potency of the embryos transferred. It is of immense help in elderly women, repeated IVF failures, cryopreserved embryos etc.