Assisted hatching is thought to aid implantation of embryos into the womb. The procedure can simply be described as thinning of the zona pellucida (the layer which surrounds the blastomeres). Under normal circumstances, proliferation of the cells causes expansion of the embryo in the blastocyst stage which eventually results in thinning and subsequently breaching of the zona layer. Implantation can occur only after breaching of the zona. The purpose of assisted hatching procedure is to aid this breaching mechanism.
Formerly thinning used to be performed by application of diluted acid solutions on the zona. Utilization of acid solutions are not as practical as application of laser which is currently widely used in most of the laboratories. The region of the zona to be thinned is easily adjusted under the microscope and shot with a laser beam. Picture on the left shows opening of the zona after one laser shot.
When to apply assisted hatching?
Although the procedure is very easy it is not used in routine practice. Assisted hatching should be used when the thickness of the zona is above limits, in thawed embryos, or in embryos from patients with recurrent implantation failure. Usually it is the embryologist and the physician who decide whether assisted hatching should be applied to the embryos of the patient.
The couples can sometimes ask for application of assisted hatching on their embryos because they have heard about its potential benefits from the newsletters, TV, etc. Assisted hatching may aid implantation of the embryo, however, it should be kept in mind that neither the quality of an embryo will improve with this technology nor an embryo with no probability will be implanted. Therefore, the couples are recommended to leave the decision to the physician and the embryologist in such issues.