Hatching ( lysis of zona pellucida) is important so that the trophoectoderm cells interact with endometrial cells and implantation occurs.
One of the reasons of failure of implantation is the inability of the blastocyst to lyse the zona pellucida (which protect the embryo after fertilization till it reaches the uterus).
So techniques were developed in order to assist the embryo in zona pellucida lysis (assisted hatching): 1- Using acid Tyrode. 2- Mechanically using a micro needle. 3- Using laser assisted hatching.
These techniques increase the pregnancy rates especially in these cases: 1- patient with previous implantation failure. 2- Frozen - thawed embryo transfer.