What is Assisted Hatching | Dr Rama Sofat Hospital

Assisted hatching is an assisted reproductive technology that is sometimes used in conjunction with conventional IVF treatment. 

Assisted hatching is thought to possibly help with the embryo implantation and is more likely to be recommended when there has been re

peated unexplained IVF failure or for patients with a poor prognosis.

How Do Embryos Hatch?

To understand assisted hatching, first, it would help to understand the natural hatching of an embryo.

Before you get an embryo, you start with an oocyte or egg. The oocyte has a protein-shell surrounding it known as the zona pellucida. The zona pellucida has many roles in embryo development, and these functions change as the embryo grows.

Before the egg becomes an embryo, the zona pellucida fuses with sperm cells. This is the start of the fertilization process. Once a single sperm cell penetrates the shell and fertilizes the egg, the zona pellucida hardens. This prevents more sperm cells from entering the now-fertilized zygote.

What Is Assisted Hatching?

During IVF treatment, fertilization takes place in the lab. But as any couple that has gone through an IVF treatment knows, having a fertilized embryo does not guarantee a pregnancy. The embryo transferred has to implant itself into the endometrium and “stick” for pregnancy to occur as explained by Dr Rama Sofat (IVF Expert).

Assisted hatching is meant to get over whatever hurdles are preventing hatching and improve the odds of implantation (and pregnancy) success.

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:

• 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. 
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•  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.
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• 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 acid. 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.
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• 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.

Risks

Any manipulation or interference with an embryo is going to involve some risk. One possible risk to assisted hatching is that the embryo will become lethally damaged. This could occur before embryo transfer or after. In either case, pregnancy would not result.

Somewhat ironically, another risk of assisted hatching is the embryo’s natural hatching process will be thrown off and the embryo will fail to fully hatch from the zona pellucida.

Another risk of assisted hatching is twinning, specifically monozygotic twinning. Monozygotic twins are identical twins, who come from one egg and one sperm. Twinning is already increased during conventional IVF treatment, and research has found that assisted hatching my further increase that risk. While all multiple pregnancies carry risk, monozygotic twin pregnancies come with even higher risks for the mother and babies. Still, the risk of twinning is low, occurring less than 1 percent of the time.

Does Assisted Hatching Improve IVF Success Rates?

The big question is, of course, is it worth it? Does assisted hatching to help you take home a baby?

Live birth rates are more important to consider that the clinical pregnancy rate since the goal in any fertility treatment is taking home a baby—not just getting a positive pregnancy test.

Unfortunately, most of the research on assisted hatching has only reported clinical pregnancy rates, and not live birth rates. Those that did look at live birth rates didn’t find an advantage. More research must be done.

Another study found that when assisted hatching was done on “good quality” embryos, pregnancy rates went down. The results varied depending on age group when assisted hatching was done on fair to poor quality embryos. This would imply that assisted hatching not only won't help those with a good prognosis, but it may harm their chances of success.

Who Might Benefit From Assisted Hatching?

There is evidence that assisted hatching may improve clinical pregnancy rates with patients who:

• Have experienced two or more failed IVF cycles
• Have poor embryo quality
• Are older than age 38

It was thought that assisted hatching might be worth trying with frozen embryo transfer cycles, but this may not be the case. In fact, one study found that assisted hatching in a frozen embryo cycle may slightly decrease the odds of a live birth.