Assisted zona hatching (AZH) is a procedure of assisted reproductive technology
in which a small hole is made in the zona pellucida, using a micromanipulation,
thereby facilitating for zona hatching to occur. Before being transferred back to
the womb a hole is made in the outer layer zona pellucida of the embryo or it is
thinned, using acid, laser or mechanical methods.
For the first 5 to 7 days of development, the embryo is surrounded and protected
by an outer shell called the zona pellucida. In normal circumstances, when the embryo
reaches the uterus, this zona partially dissolves and the embryo ‘hatches’ out,
allowing it to implant in the uterus. In some patients it is thought that infertility
may be caused by a hardening of the zona, which makes it difficult for the embryo
to hatch and implant. Assisted hatching is a laboratory micromanipulation technique
carried out before the embryos are replaced in the uterus that helps the embryo
to hatch from the zona.
Hatching is a process by which the fully developed embryo comes out of its shell
(zona pellucida) and starts communicating with the uterus. Under certain circumstances,
like thick shell, (in case of endometriosis or due to defective oogenesis), hardened
shell (frozen-thawed embryos) etc. artificially starting the hatching process helps
embryo to implant. In this process, part of the shell is chopped off carefully using
laser machine.