The embryo is surrounded and protected by the zona pellucida. Normally, when the blastocyst reaches the uterine cavity, an opening is created in the the zona pellucida in order for implantation to take place. Assisted zona hatching is another micromanipulation technique during which, on the day of embryo transfer, a small opening in the outer part of the embryo is made in order to facilitate embryo hatching from overly thick or hardened zona pellucida, thus increasing the chance for implantation and pregnancy. The opening is either made by using chemical solutions (Tyrode’s Acid), mechanically using micropippetes, or using short pulse laser beam.

Scientific data regarding the success of the method is debatable. In a minority of cases results are good, but usually assisted zona hatching does not help, and can even harm the embryo.