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Artificial Weakening of Embryo Shell (Assisted Hatching)

Assisted Hatching or artificial weakening of embryo shell, is one of the auxiliary methods used to increase the success rate of IVF treatment. It is practiced to facilitate the placement of the embryo in the uterus and increase the chances of pregnancy.¹

For a better understanding of the technique, it is beneficial to refer to the process before embryo formation.

The egg has a shell made of protein called zona pellucida that surrounds it. For the formation of an embryo, sperm must penetrate the zona pellucida. The penetration of the sperm cell into the zona pellucida is the beginning of the fertilization process.

When the sperm crosses the shell and merges with the egg, the shell hardens. Because of this hardening, other sperm are prevented from entering the egg.² The zona pellucida continues to surround the fertilized egg. Under normal conditions, when the embryo approaches the blastocyst stage, the shell expands, begins to thin out, and its structure deteriorates. Thus, the embryo is prepared to settle in the uterus.

In cases where the embryo cannot get rid of its outer shell, pregnancy is not possible since implantation cannot occur. The technique, which we can define as weakening the shell by opening a hole in the embryo shell, is an intervention that will facilitate the placement of the embryo in the womb. With different techniques performed in the laboratory, the probability of the embryo getting rid of the shell that it is surrounded with, can be increased.

How is the Embryo Shell Weakened?

Different techniques can be applied to weaken the shell surrounding the embryo. It is possible to weaken the shell mechanically, using an acidic solution or by using laser.

In the mechanical hatching technique, the embryo is held stable with the help of a pipette, and a micro-needle is used to pierce the zona pellucida. The disadvantage of the technique is the difficulty of controlling the size of the hole pierced in the shell.
In the chemical hatching technique, a small amount of acid is applied on the shell. When the targeted opening is achieved, the embryo is quickly cleaned. It is important to perform the cleaning process quickly and effectively in order to prevent any damage to the embryo.
In the laser assisted hatching technique, a hole is created in the embryo shell using laser beams. The advantage of this technique is that it provides higher control over the dimensions of the created hole.

Regardless of the preferred technique, the weakening of the embryo shell is a procedure that must be performed with extreme sensitivity. The probability of damaging the embryo, though quite small, is still there.³ It is known that the risk of complications is higher in monozygotic twin pregnancies.⁴

Who can benefit from Assisted Hatching?

Assisted Hatching method is one of the auxiliary treatments that can be used optionally with the IVF treatment. The eligibility requirements for assisted hatching, which can increase the probability of pregnancy can be listed as follows;

Failure of more than two IVF attempts,
Poor embryo quality,
Expectant mothers being 38 and over⁵

¹ https://www.reproductivefacts.org/news-and-publications/patient-fact-sheets-and-booklets/documents/fact-sheets-and-info-booklets/assisted-hatching/
² https://www.verywellfamily.com/assisted-hatching-and-ivf-risks-possible-benefits-4156886
³ https://www.hfea.gov.uk/treatments/treatment-add-ons/assisted-hatching/
⁴ https://www.hopkinsmedicine.org/gynecology_obstetrics/specialty_areas/fertility-center/infertility-services/assisted-hatching.html
⁵ https://www.verywellfamily.com/assisted-hatching-and-ivf-risks-possible-benefits-4156886

Artificial Weakening of Embryo Shell (Assisted Hatching)

How is the Embryo Shell Weakened?

Who can benefit from Assisted Hatching?

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