The technique of assisted hatching involves measuring the thickness of the zona pellucida in embryos that are candidates for the procedures. If an embryo has not initiated the thinning process naturally, a small “window” is created chemically in the wall of the protein coat, using a dilute acidic solution pulsed onto the embryo surface, through an extremely fine glass micromanipulation needle. The embryos are then implanted normally into the uterine cavity.
You may be a candidate for assisted hatching if you are 36 years of age or older, or if you have previously had one or more IVF cycles, with failure of your embryos to implant, despite otherwise good results.
In order for the embryo to implant in the uterus , it has to first escape from its outer shell (the zona pellucida). Certain patients and women of 37 years and older may produce embryos with shells that have become hardened, therefore, preventing the embryo from implanting in the uterus. To help the embryo escape from its shell, we sometimes recommend a procedure called assisted hatching . With this procedure, we create a small opening in the outer layer of the embryo before the transfer.
It has been proposed that a certain number of otherwise viable embryos do not implant simply because they are unable to break free from the surrounding “jelly coat” (zona pellucida) when they reach the blastocyst stage of development. Around an unfertilized egg there exists a transparent glyco-protein coat that acts to protect the egg and regulate normal fertilization by any penetrating sperm. This jelly-like coat continues to protect the early preimplantation embryo until, as a blastocyst, the embryo fills itself up with fluid like a water-filled balloon, pumping itself larger and larger until it ruptures and “hatches” from the zona pellucida. The embryo is now ready to make contact in its naked form with the endometrium and implant. Inappropriate ovarian environment due to advanced maternal age or other factors that may compromise the follicular environment may in certain cases render the zona pellucida thicker or tougher.
Such IVF cases may benefit from the application of a form of micromanipulation referred to as “assisted hatching” In this process, the embryo has a hole made in the surrounding zona pellucida prior to transfer to enable it to “hatch” free from the zona pellucida more easily when it expands as a blastocyst in the uterus. This technique has never been unconditionally proven to be effective in any well-defined group of IVF patients, and as such remains essentially an experimental procedure. Holes in the zona pellucida may be made mechanically, chemically, or by laser. With the advent of more routine transfer of blastocyst stage embryos, the future of this technique, usually carried out on day three of development, may seem in question. Indeed, at the blastocyst stage in vitro, it may be most appropriate to dissolve off the entire zona pellucida prior to transferring naked embryos into the uterus. This could be considered the ultimate form of assisted hatching without the need for micromanipulation. Currently, however, assisted hatching can be easily performed using a infrared laser to create a hole in the zona pellucida that allows the embryo an easy means of escape when it is time to try and implant into the uterine wall.