Assisted Hatching

During the initial stages of development, your embryo is contained in a "shell" or layer of proteins, known as the zona pellucida. The zona pellucida is designed to protect the embryo until it reaches the blastocyst stage of development. In order to successfully implant into the uterine lining, the embryo needs to "hatch out" of this zona pellucida and attach to the walls of the uterus.

In certain situations, the zona pellucida (the outer shell or wall surrounding the embryo) is abnormally thick and/or hardened. If this is the case, than it may make it difficult or impossible, for an otherwise normal embryo, to break out, or hatch, from the zona pellucida at the time of implantation. This condition, would then compromise the ability of the embryo to implant in the uterine wall. This situation is improved with assisted hatching (AH). AH is a procedure where a microscopic hole is made in the zona pellucida using micromanipulation techniques. At the same time as AH, any lysed or dead cells are also removed from the embryo (lysed cell removal or LCR). The literature suggests that these dead or lysed cells may be toxic to the embryo and their removal improves implantation and pregnancy rates. Although AH can be done on fresh embryos, the current literature does not show improved implantation and pregnancy rates with routine AH, except in very specific situations like advanced maternal age, where there is an increase possibility that the wall of the embryo can be hardened, although the embryo itself is fine, elevated FSH levels or failed attempts at prior fresh IVF cycles. The literature does support, however, improved implantation and pregnancy rates when AH and removal of lysed cells are used on cryopreserved embryos that are transferred on day 3.Cryopreservation may artificially hardened the wall of the embryo. ACFS recommends that AH be done on all frozen embryo transfers.

To date there appears to be no adverse effects of AH on the embryo and the future offspring. To date, ACFS embryology laboratory has not injured a single embryo doing AH.

ACFS criteria for recommending assisted hatching (AH).

1. Maternal age of 38 or older
2. Elevated levels of FSH
3. Previous one unsuccessful attempt at IVF
4. Frozen-thawed embryos for transfer

How is assisted hatching performed?

1. The embryo is held with a specialized holding pipette (on the left).
2. A very delicate, hollow needle is used to expel a mild acid solution against the outer "shell" (zona pellucida) of the embryo (on the right).
3. A small microscopic hole is made in the shell by digesting it with the acid solution.
4. The embryo is then washed and put back in culture in the incubator.
5. The embryo transfer procedure is done shortly after the hatching procedure.

Risks Associated with Assisted Hatching

Unfortunately, there are some risks associated with AH/LCR: It is possible to damage embryos with hatching and lower the pregnancy rate.

Therefore, it is essential that if assisted hatching is done, it must be performed by properly trained embryologists.

There is some evidence to suggest AH may increase the risk of identical twins.

Rare complications would include complications to the fetus, physical deformity and conjoined twins. The actual pregnancy and live birth rates seen in an individual IVF center will vary according to the hatching technique used, the overall quality of the embryology laboratory, the experience and expertise of the individual performing the hatching, the embryo transfer skills of the physician, and other factors. The current data shows that there appears to be no adverse effects of AH on pregnancy rates and the future offspring. To date, ACFS embryology laboratory has not injured or lost a single embryo doing AH.