In vitro fertilization (IVF) failure is a frustrating experience for individuals and couples, and it is often caused by an embryo's failure to implant in the uterus. For women who have failed IVF or have a poor prognosis for IVF, the fertility doctor may recommend a technique known as assisted hatching.
After an egg is fertilized in the laboratory, the cells begin to divide. During these initial stages of development, the embryo is contained in a layer of proteins known as the zona pellicuda. In order to successfully implant into the uterine lining, an embryo has to hatch out of the zona pellucida and attach to the walls of the uterus.
Assisted hatching is a newer lab technique that was developed when fertility experts observed that embryos with a thin zona pellucida had a higher rate of implantation during IVF. With assisted hatching, an embryologist uses micromanipulation under a microscope to create a small hole in the zona pellucida.
At present, there are three methods that can be used to improve the hatching of embryos selected for transfer: (i) the mechanical technique, i.e. partial zona dissection using glass microneedles; (ii) chemical assisted hatching, using acidic Tyrode's solution; and (iii) laser-assisted hatching.
Mechanical technique(partial zona dissection) : The zona pellucida is pierced with a very thin glass microneedle through both sides, the needle tip position being controlled in the perivitelline space by eye. Then the suction of the holding pipette is stopped and the holding pipette is rubbed against the trapped area of the zona until this area has been completely abraded.
Acidic Tyrode's assisted hatching : The fine micropipette containing acidic Tyrode's solution is brought very close to the zona pellucida and the acidic solution expelled gently over a small area (-20-30 gm) until the zona is dissolved through to the inside. After the procedure, the embryos are thoroughly washed in fresh medium and cultured until the time of transfer.
Laser assisted hatching : The laser has been shown to be efficient and safe in humans to carry out zona pellucida drilling for assisted hatching as well as for polar body or blastomere biopsy. Recently, infrared diode-laser light focused through a microscope objective has enabled rapid non-touch microdrilling. Embryos are maintained in their culture medium. Special care should be taken to open the internal side of the zona. No washing of the embryos is needed after laser drilling. This procedure appears to be quick, precise and is chemical free.
Assisted hatching is thought to be helpful for couples with a poor prognosis whose embryos are thought to lack sufficient energy to complete the hatching process. assisted hatching may be indicated for women with:
Assisted hatching has been found to help with IVF success in poor prognosis patients.Couples with multiple failed IVF cycles also benefited from assisted hatching.