Assisted hatching is a micromanipulation technique used to assist the implantation process during IVF and carried out by an embryologist in the laboratory.
With this technique, a break is created on the outer layer of the zona pellucida by an experienced embryologist using a very fine needle or laser under a very high-powered microscope. Assisted hatching helps the embryo to hatch from the zona.
What is Assisted Nesting?
In most couples undergoing infertility treatment, pregnancy does not occur despite embryo development. The most important reason for pregnancy not occurring despite fertilization is usually a problem with the embryo settling in the uterus.
Various changes occur after the embryo is placed in the uterus. The embryo continues to grow and divide. When it reaches a certain size, it tears the membrane surrounding it, known as the zona pellucida, and settles deep into the endometrium, where it continues its development. This situation is called “hatching”.
The general view regarding the failure of pregnancy is that the embryo cannot break the zona pellucida membrane and cannot come out and settle in the uterine wall. In order to eliminate this problem, a small hole is opened in the membrane surrounding the embryo with chemical or mechanical methods before the transfer process. In this way, the embryo is allowed to tear the membrane and settle in the uterine wall. Assisted implantation is a technique used to help couples who have had one or more unsuccessful IVF cycles in the past.
Before undergoing assisted implantation, it is important to understand how implantation occurs. In a natural pregnancy, an egg is released by the ovaries and fertilized by a single sperm to form an embryo. This embryo is surrounded by a tough outer layer of cells called the zona pellucida. In order for the embryo to implant into the uterine wall, it must break free from this outer “shell.” The zona pellucida is often thicker than normal and may need to be manually stimulated to separate from the embryo. Therefore, assisted implantation may be used.
During an IVF treatment, eggs and sperm are combined in the laboratory to increase the chances of successful fertilization. The embryos are monitored for several days while an embryologist makes a small crack in the zona pellucida to help release the embryo for implantation. Assisted implantation is performed on the third day of embryo development.
Assisted hatching is recommended for patients undergoing a second or third IVF treatment due to unsuccessful cycles. It can also be used for couples who are unable to conceive naturally due to various medical conditions or reproductive damage. Other situations where assisted hatching may be beneficial include:
- Women over the age of 36 may benefit from assisted hatching because the zona pellucida can thicken with age. Over time, the number of eggs decreases and egg quality can cause fertility problems.
- Repeated IVF cycles are often unsuccessful, whether the cause of infertility is explainable or unexplained. Assisted hatching can increase the chance of a successful pregnancy even in an unexplained condition.
- Abnormalities in the structure of the zona pellucida can hinder the chance of successful implantation. The thick or hard protective shell surrounding the embryo may be linked to increased levels of follicle-stimulating hormone (FSH).
- Using previously frozen embryos can create difficulties in fertilization. Assisted hatching is performed on thawed embryos because the zona pellucida can harden during cryopreservation.
- Since IVF treatment is personalized for each patient, assisted hatching is designed to help with a range of medical issues. These include issues such as excessive fragmentation, slow cleavage rates, and embryo-related conditions.
There are many pros and cons to assisted hatching. Assisted hatching is known to increase the rate of successful implantation and pregnancy. Up to 38% of embryos created through assisted hatching result in pregnancy, while the implantation rate can be as high as 50%.
However, it should not be overlooked that, like any other medical procedure, assisted hatching carries some risks. Successful assisted hatching depends not only on the response of the embryo, but also on the skills of the embryologist performing the procedure. If the technique is not perfect or if the zona pellucida is handled poorly, the embryo can be damaged.
Assisted hatching can weaken the protective shell of the embryo to the point where it can become infected. Pregnancy can result in multiple births or, in extremely rare cases, birth defects.
