Assisted Hatching
What is Assisted Hatching?
Assisted hatching is an additional procedure that can be performed in patients who are undergoing in vitro fertilization (IVF) treatment. Once embryos are created using IVF (IVF process timeline), the embryo is surrounded by a hard outer layer of cells called the zona pellucida. You can think of this outer layer as the “shell” of the embryo. An embryo must break free of this “shell” in order to implant into the uterus and develop into a pregnancy.
Assisted hatching is a procedure where we can help the embryo “hatch” from its “shell” by creating a small crack in the zona pellucida. It is believed that assisted hatching can help an embryo implant in the uterus, leading to higher pregnancy rates in some patients.
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Before Assisted Hatching
Who are ideal candidates for assisted hatching?
Several factors can make someone a candidate for assisted hatching with in vitro fertilization.
. Patients who have experienced previous failed IVF cycles.
. Patients whose embryos are not developing as well as expected.
. Patients transferring frozen-thawed embryos – hardening of the zona pellucida has also been attributed to the freezing procedure.
. Patients with raised follicle stimulating hormone (FSH) and reduced ovarian reserve.
. Patients older than 38 can all benefit from assisted hatching.
Since there are no known downsides, and the potential for increased implantation rates exists, we believe that all IVF patients can benefit from our advanced assisted hatching techniques.
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Risks
What are the risks associated with Assisted Hatching?
During the early stages of embryo development, the outer shell (zona pellucida) serves as a protective barrier against foreign bodies. As assisted hatching involves breaching the outer shell, there are some extremely small risks associated with this procedure. These include:
. The developing embryo being exposed to harmful chemicals and micro-organisms.
. Further embryonic development may be affected, or the cells within the embryo may be expelled through the drilled hole and thereby causing the embryo to perish.
. The process of laser hatching has a very small risk of cell damage due to localized heat being applied to facilitate the opening in the zona pellucida.
. There is also an additional small risk (2%) that this procedure could entrap the embryo during the hatching process causing monozygotic twins (identical).
During Assisted Hatching
Assisted Hatching Methods
You may assume that assisted hatching always involves making a small “break” or tear in the zona pellucida. But that’s not actually so. There are a few methods available, and every embryo lab approaches this differently.
There are pros and cons to every way, and the skill of the technician matters. Be sure you gather as much information as possible so that you can make an informed decision.
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. Mechanical hatching: With this technique, the embryologist keeps the embryo steady with the help of a pipette, while using a micro-needle to puncture through the zona pellucida, go just underneath the shell for a bit, and then come out the other end. (Imagine drawing a very thin line just alongside the embryo.) Then, the area between the two punctures is gently rubbed until a small tear occurs. It’s difficult to control the size of the opening with this method.
. Mechanical expansion of the shell: With this technique, the zona pellucida is not broken open. Instead, hydrostatic pressure is introduced just under the shell, to cause it to expand. The idea for this method comes from the natural expansion of the outer shell during the hatching process.
. Chemical hatching: This technique involves using a chemical known as Tyrode’s solution. Tiny amounts of acid are applied to the zona pellucida until the shell is breached. Then, the embryo is quickly cleaned to avoid unnecessary acid exposure.
. Drilling: With drilling, vibratory movements are used to create a conical opening. This technique uses something known as Piezo technology.
. Laser-assisted hatching: Using a specialized laser to breach the zona pellucida is another possibility. Laser-assisted hatching allows much more control of the size of the hole created, more so than mechanical hatching with a needle (as described above).
Of all the methods, laser-assisted hatching may be the safest and most effective. However, not every embryology lab is equipped to perform this specific technology. Chemical hatching is more commonly used. With all of these methods, the skill and experience level of the embryologist can make a big difference.
What is Laser-assisted Hatching Process?
Here are the steps we use for the laser assisted egg hatching process:
- There are frequently several steps along the journey from egg retrieval to embryo transfer. The majority of IVF our cases are frozen embryo transfers, and most of our patients elect to have PGS performed. All of this happens before assisted hatching.
- Immediately prior to transfer, the embryo is moved to our micromanipulation station.
- We use an automated witnessing tool, called RI Witness, to verify that all laboratory procedures are performed on your embryo, virtually eliminating the risk of mixing up your embryo with another patient.
- Your embryo is then placed on the inverted microscope of the micromanipulation station, where our experienced embryologists determine the best location to perform laser assisted hatching.
- Using these measurements, the location, focus, and intensity of the laser adjusted to ensure minimal heat exposure of nearby cells.
- The laser creates perforations in the zona by vaporizing it. Typically, two or three laser pulses are delivered to create the gap.
- Once laser assisted hatching is complete, the embryo is returned to culture medium and placed in the incubator to await transfer.
How is assisted hatching performed using acid Tyrode’s solution?
- The embryo is held with a specialized holding pipette.
- A very delicate, hollow needle is used to expel the acidic solution against the outer “shell” (zona pellucida) of the embryo.
- A small hole is made in the shell by digesting it with the acidic 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.
- Embryo transfer places the embryos in the uterus where they will hopefully implant and develop to result in a birth.
After Assisted Hatching
Pregnancy rates
Pregnancy rates for in vitro fertilization procedures with assisted hatching have been shown in some published studies to be higher than for IVF without hatching. There is an improvement in the rate of embryo implantation and pregnancy in our IVF clinic with the use of assisted hatching. Apparently, this benefit is not seen in all IVF programs.
It is possible to damage embryos with hatching and lower the pregnancy rates. Therefore, it is essential that if assisted hatching is done, it must be expertly performed by properly trained embryologists.
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 laboratory, the skill of the individual performing the hatching, the embryo transfer skills of the physician, and other factors.
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