AZH is a micro-surgical technique performed on embryos to increase the probability of implantation and therefore pregnancy. When an embryo reaches the blastocyst stage it has to hatch from its surrounding protective coat the zona pellucida in order to make contact with and implant into the uterus. In the normal course of events this process is enzymatic, with the enzymes being produced by the embryo. If this process is defective for any reason implantation will fail. Using a special laser our embryologists may aid this process by drilling a small hole in the protective coat helping the embryo to hatch. AZH is particularly recommended when the zona pellucida appears too thick, for women over 38 years of age and when the patient has had several failures at implantation.