Assisted hatching is a laboratory technique designed to enhance implantation of embryos generated through in vitro fertilization (IVF). Combined with fragment removal, this technique is thought to promote development of embryos adversely affected by fragmentation.
Fragmentation is found in some 80% of IVF embryos, and it implies that sometime during the process of division, pieces of cytoplasm have been lost from the dividing cells. Although the exact causes of fragmentation are not known, this phenomenon may be linked to extrinsic factors such as in vitro culture conditions. The inherent properties of the eggs and sperm that created the embryo can also contribute to fragmentation. Judging by its prevalence, some forms of this phenomenon may be a part of normal development, however, it is clear that significant fragmentation interferes with implantation and pregnancy and could be a cause of infertility.
Assisted hatching and fragment removal together may restore a compromised embryo’s development potential to become a fetus (baby). Candidates for this procedure are chosen based on the female’s age, the presence of elevated follicle stimulating hormone, degree and pattern of fragmentation found in the embryos, the thickness of the zona pellucida (the protective outer shell of the egg that remains until implantation) and/or the number of previously attempted IVF cycles.
Assisted Hatching Procedure
Assisted hatching is a micromanipulation technique developed to help embryos “hatch” or escape from the zona pellucida. Hatching is a pre-requisite to implantation and normally a process carried out by the embryo itself. During assisted hatching, while the embryo is held on a holding pipette (a fine glass tube), a micro-needle is loaded with an acidified solution. The solution is quickly and gently applied to a small area of the zona pellucida until the area is dissolved, creating a tiny hole and providing the embryo with an artificial “escape route”.
The Fragment Removal Procedure
Fragment removal is an extension of the assisted hatching technique. After the hole is made in the zona, the same needle is used to aspirate all or most of the fragments within the embryo. Fragment removal is performed on the third day of development, prior to replacement of embryos in the uterus.