The embryo is developed to a certain size in a solid membrane. If pregnancy is to occur, the embryo must leave this membrane once it is transferred to the uterus. The purpose of assisted hatching is to create an opening in the solid casing of the embryo before it is transferred to the uterus. The application of this method increases the likelihood of pregnancy. It is the embryologist who decides if this method should be applied by analysing the development of the embryo and upon the consent of the treated couple.