One of the most frustrating aspects of assisted reproductive technology for patients and fertility professionals alike is having to deal with failure. This is especially true in couples who have attempted assisted reproductive procedures many times, and also in those whose time is running out because of their age. Now, a recently developed technique, assisted hatching, is offering new hope to couples who fall into these categories.
Assisted hatching was developed from the observation that embryos which had a thin zona pellucida (shell) had a higher rate of implantation during in vitro fertilization. It was postulated that creating a minor defect in the zona might result in a greater chance of the embryo “hatching,” or shedding its shell, allowing for a better chance of implantation in the endometrium.
Initial controlled trials at New York-Cornell Medical College showed a marked increase in implantation in women over age 35 and particularly over 38 or with an elevated FSH level on day 3 of the menstrual cycle. Couples with multiple failed IVF cycles also appear to benefit from assisted hatching. Assisted hatching may be helpful in these infertile couples because their embryos lack sufficient energy to complete the “hatching” process. It is thought that some women may fail multiple cycles of IVF because their eggs have a thicker shell, therefore they have a better prognosis with assisted hatching. In addition, hatched embryos implant one day early, which may allow a greater opportunity for implantation to occur.
The addition of assisted hatching to the standard IVF protocol does add extra laboratory manipulation and therefore added costs. There is a small risk of damage to the embryo during the micromanipulation process or at the time of transfer, and there is a slight increase in identical twinning . There is a greater chance of fetal complications and abnormalities in some identical twins. A rare complication of identical twinning is conjoined or “Siamese” twins. We have not observed a higher rate of identical twins than with routine IVF. This may relate to whether a large enough opening is made in the zona to prevent pinching of the embryo during the hatching process.