People do not often associate egg hatching with human development, yet the process of an embryo implanting in the uterus is similar. Before it can implant, the embryo must break through a protein coating or “shell” that surrounds it. This coating is called the zona pellucida. When it is too thick, the embryo is unable to break through, which prevents implantation.
In assisted hatching, the embryologist weakens the zona pellucida or creates a tiny hole using a laser while the embryo is being cultured in the lab. In some instances, an acid solution called Tyrode’s solution is used to help melt a small hole in the coating. This procedure is usually carried out on the third day of embryo development. Weakening or “cracking the shell” allows the embryo to continue growing while increasing its chances of breaking through the coating and implanting in the uterus.
