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). Assisted hatching is a procedure where a microscopic hole is made in the zona pellucida using micromanipulation techniques. At the same time as assisted hatching, 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 assisted hatching can be done on fresh embryos, the current literature does not show improved implantation and pregnancy rates with routine assisted hatching, 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 in vitro fertilization cycles.
The literature does support, however, improved implantation and pregnancy rates when assisted hatching and removal of lysed cells are used on cryopreserved embryos that are transferred on day 3. Cryopreservation may artificially harden the wall of the embryo. Arizona Center for Fertility Studies recommends that AH be done on all frozen embryo transfers.
To date there appears to be no adverse effects of assisted hatching on the embryo and the future offspring. To date, Arizona Center for Fertility Studies embryology laboratory has not injured a single embryo doing assisted hatching.
Criteria for Recommending Assisted Hatching (AH)
- Maternal age of 38 or older
- Elevated levels of FSH
- Previous one unsuccessful attempt at In Vitro Fertilization
- Frozen-thawed embryos for transfer
How is Assisted Hatching Performed?
- The embryo is held with a specialized holding pipette (on the left).
- 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).
- A small microscopic hole is made in the shell by digesting it with the acid solution.
- The embryo is then washed and put back in culture in the incubator.
- The embryo transfer procedure is done shortly after the hatching procedure.
Picture of the micropipette, on the right, making a small hole in the
zona pellucid or wall of a day 3 embryo.
Laser Assisted Hatching
The advent of the laser has allowed the development of precision techniques to manipulate embryos for enhanced fertility. Laser-assisted hatching (LAH) can potentially enhance implantation/pregnancy rates or turn around a history of failure for embryos to implant themselves in the uterine wall. Arizona Center for Fertility Studies strongly believes that laser technology is state of the art technology for any embryos that undergo assisted hatching (AH), embryo biopsy for chromosome abnormality/single gene mutations or gender or sex selection and prior to transferring cryopreserved or frozen embryos (FET). Arizona Center for Fertility Studies embryologist, Andrew Barker, is one of a number of reproductive embryologists in the country that is highly skilled in using the laser on human embryos.
Assisted-laser hatching (LAH) is used to help the embryo hatch from its protective outer shell, the zona pellucida, and promote implantation in the uterine wall after embryo transfer. LAH uses a highly focused infrared laser beam to remove a very small section of the zona pellucida, or outer wall of an embryo, in very precise increments. Prior to the clinical availability of the laser-assisted hatching, only mechanical or chemical methods (acid) could be used for assisted hatching of human embryos in clinical settings. Laser-assisted hatching requires less handling of the embryo than these other assisted hatching methods. Also, laser-assisted hatching is faster than the other methods and, therefore, the embryo spends less time outside the incubator.
Arizona Center for Fertility Studies strongly feels that LAH (laser assisted hatching) improves the success rates of implantation and subsequently in vitro fertilization; and therefore all embryos, transferred at ACFS, undergo assisted hatching (AH) with the laser. Since Arizona Center for Fertility Studies only does day 5/6 blastocyst transfers, all blastocysts that are transferred will undergo laser assisted hatching. Since cryopreservation may artificially harden the wall (zona pellucida) of the embryo, all thawed embryos also undergo laser assisted hatching prior to transfer.
Picture of a day 3 eight-cell embryo about to undergo laser-assisted hatching (arrow, round marker, indicates where the laser beam will penetrate the zona pellucida)
Risks Associated with Assisted Hatching
Unfortunately, there are some risks associated with Assisted Hatching / Lysed Cell Removal: 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 assisted hatching 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 in vitro fertilization (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, Arizona Center for Fertility Studies embryology laboratory has not injured or lost a single embryo doing assisted hatching.