Eggs and embryos have an outer shell known as the zona pellucida. Before an embryo can implant into the lining of the uterus it must "hatch" out of this shell. This usually occurs five or six days following fertilisation. The most common reason for an IVF or ICSI cycle to fail is because embryos fail to implant.
There are many reasons why successful implantation does not occur. One of these reasons may be due to the fact that the embryo is unable to "hatch" because the zona pellucida is too thick or hard. Assisted hatching is a laboratory procedure whereby a hole is made in the zona pellucida of a two or three-day old embryo in order to help in the " hatching" process and, therefore, help with the implantation of the embryo into the uterus.
Several techniques including a laser, chemical or a very sharp needle can be used to make a hole in the zona pellucida. The first assisted hatching techniques were carried out in the early 1990’s. Most IVF clinics use this procedure and many babies have been born as a result of assisted hatching and there have been no reports of an increase in abnormalities of babies born as a result of assisted hatching.