Author Name: Dr. Arnab Barma Mentor Name: Dr. Amol Naik on April 08, 2020
Assisted hatching is a laboratory micromanipulation technique carried out before the embryos are replaced in the uterus following an IVF or ICSI cycle that helps the embryo to hatch from the zona.
In natural conception mixing of eggs and sperm occur within a women’s body whereas in IVF it occurs in a Laboratory and hence the name Test Tube Baby. When a sperm penetrates the egg, the egg is fertilised. During IVF, the fertilized eggs are monitored for 3 to 6 days as they divide and develop into embryos. For the first 5 to 7 days of development, the embryo is surrounded and protected by an outer shell called the zona pellucid. Normally when the embryo reaches the uterus, this zona partially dissolves and the embryo hatches out and implants in the endometrial lining of the uterus. In some patients the zone becomes so hard that it becomes difficult for the embryo to hatch and implant.
Sometimes, the doctor may ask the embryologist to make a small “Hole” in the outer shell of the embryo right before it is placed into the woman’s uterus. The assisted hatching might help the embryo expand, implant into the uterine wall, and finally lead to a pregnancy. The reason is to place the best embryo into the woman’s womb and helping her become pregnant or it can be frozen for future use.
• Woman is aged 35 years or older
• Couples having failed previous IVF cycles
• Woman having high FSH levels during follicular phase
• Frozen embryo replacements
• Thickened zona noted by embryologists
• Embryos not developing well as expected.
There is a slight increased risk for identical twins and hence medical complications are higher than in normal, singleton pregnancies.
Assisted hatching can damage the embryo very rarely and hence it has to be discarded.
Sometimes antibiotics and steroid hormones are prescribed around the day of embryo transfer with assisted hatching which may uncommonly cause side-effects.
All patients who are undergoing IVF treatments to conceive are not recommended for the use of assisted hatching techniques.There are some research suggesting that assisted hatching might help improve pregnancy chances for certain groups of patients like in women who have failed to get pregnant in previous IVF cycles and those who are not likely to conceive(i.e. having poor prognosis).
When preimplantation genetic diagnosis (PGD) is planned, assisted hatching of embryos on the third day after fertilization can make a biopsy for PGD easier. During a biopsy, a small amount of tissue is taken from the outer cells of the embryo (trophectoderm) around the fifth day after fertilization (blastocyst stage). It is easier to see the trophectoderm and remove the cells in a hatching embryo.
Assisted hatching is performed immediately before embryo transfer. Although the goal of each technique is to weaken or perforate the zonapellucida but the differences in methodology and results are significant.
There are Four methods for IVF Assisted Hatching:
• Laser assisted hatching is a more modern approach. In this method, the thickness of the zona is measured and Laser shots are applied to thin out the zona in a controlled way by photoablation. It is one of the safest method and with experience the embryologists can perform the procedure with more speed and precision than other methods.
• Acid Tyrode’s solution is added onto the zona through a micro needle. A specialized holding pipette is used to restrict the movement of the embryo. The acid melts away the zona creates a small hole and it goes into the embryo. Then the embryo is washed and placed back in culture medium and reincubated until the time of embryo transfer. It is the most common method but there is a potential to introduce acid into the developing embryo.
• Partial zona dissection (PZD) is a mechanical method that creates a cross-hatched slit in the zona. The embryo is held with a holding pipette and a microneedle pierces the zona tangentially from 1o’clock to 11o’clock position. The embryo is then released from the holding pipette and part of zona between these two points is rubbed against the holding pipette to make a slit in the zona. The embryo is then washed twice and kept back in culture medium. There is a chance for creation of larger openings in this technique.
• Piezo Technology is a method where the embryo is held with a holding pipette, vibratory movements are produced by a piezo-electric pulse used to carve a limited conical area in the zonapellucida.5 to 8 applications used to produce a large hole.
The assisted hatching methods increase the chance of implantation of transferred embryos. Though laser assisted hatching is the best among all methods but there is no concrete proof in favour of it.
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