What is assisted hatching, and does it increase the chance of pregnancy? The level of evidence, multiple pregnancy risk and questions to ask your doctor.
Assisted hatching is the thinning or opening, in the laboratory, of the outer shell called the zona pellucida that surrounds the embryo. Current assessments on this subject do not recommend its routine use. A review could not show a clear benefit for live birth and reported a possible increase in multiple pregnancy; the reliability of this finding is low. This does not mean that the procedure is ineffective; it means that its benefit has not yet been shown. You can talk with your doctor about whether the practice will be considered for you.
Which part of the embryo is intervened on in assisted hatching?
The zona pellucida is the protective outer shell that surrounds the egg and, in the first days, the embryo. In natural development the embryo comes out of this shell before attaching to the lining of the uterus. The method aims at thinning or opening the shell with the purpose of helping this process.
By which methods is assisted hatching performed?
The procedure can be performed with acid, a laser or other instruments. The device and technical details vary with the centre.
Does advanced age or a previous failure show that you will benefit from this procedure?
Repeated failure, advanced age and a thick zona are mentioned as reasons for the practice. It has been put forward that it may be useful in these groups, but sufficient data to support this could not be found. According to current guidelines on this subject, the data supporting this recommendation in groups with a poor prognosis are also insufficient.
Is assisted hatching recommended for everyone?
According to current guidelines on this subject, laser-assisted procedures should not be recommended routinely to all IVF patients. The data available are also not enough to distinguish which group of patients would benefit from the procedure. Consequently the practice is an option that is considered according to your doctor's clinical approach, and its benefit has not been demonstrated by studies.
Does assisted hatching increase the chance of live birth?
A systematic review assessed many controlled studies together. No clear benefit could be shown for live birth; a small increase in clinical pregnancy was reported, but the reliability of this finding is low, and depending on the analysis method used, no difference or very little may be found. Its effect on pregnancy loss is uncertain.
Do current assessments recommend the procedure?
In current good practice recommendations on this subject, assisted hatching is in the category of "not recommended". The reasons given are that no marked difference could be shown in live birth and that multiple pregnancy increases; a concern about identical twinning has been voiced, but the number of cases was found to be insufficient to reach a definite conclusion. Another current guideline also states that there is moderate evidence that it does not significantly increase live birth in fresh cycles.
Why is the possible increase in clinical pregnancy not considered sufficient?
The small increase in clinical pregnancy and the uncertainty in live birth belong to the same picture; the review assessed the reliability of this evidence as low. Because there are no strong data on subgroups, it cannot be said either that the method works in one group or that it does not. The outcome of IVF is also affected by many factors, such as your age and the number and quality of the embryos.
Can the procedure harm the embryo?
According to assessments done, the procedure carries no known additional risk for you; however, there is a possibility of harm to the embryo.
What is known about multiple pregnancy and identical twinning?
In a review it was reported that multiple pregnancy might be increased; this increase is regarded as a complication. A concern about identical twinning has been voiced, but it is stated that the number of cases is insufficient to reach a definite conclusion. In another assessment, the evidence for an association with identical twinning was found insufficient, because it is a rare outcome and the studies contradict one another. Multiple pregnancy can increase risks such as preterm birth.
Could there be an additional fee?
An additional fee may be requested for the practice; you should discuss openly with your doctor whether you will pay for a procedure whose benefit has not yet been shown.
The procedure is performed on the embryo in the laboratory; it involves no separate intervention for you.
Is assisted hatching the same as embryo biopsy?
No. Embryo biopsy is the taking of cells from the embryo for genetic examination (PGT) and is a separate procedure. The purposes of the two practices are different. You can clarify with your doctor and embryologist which one is planned.
What can you ask your doctor when the procedure is recommended?
- What is the reasoning for recommending assisted hatching?
- By which method, and on which embryos, will the procedure be applied?
- What would change in my treatment plan if it were not done?
- Is a separate fee charged for the procedure?
- How is this procedure described in the document I will sign?
Frequently Asked Questions
Is assisted hatching done on a frozen embryo?
According to current guidelines on this subject, there are not enough data to recommend the practice in the transfer of frozen-thawed embryos. That is, in this case too, no clear conclusion on its benefit or harm can be stated. You can ask your doctor whether it will be applied and the reasoning.
What does the "grey" classification of regulators mean?
The regulator in the United Kingdom classifies assisted hatching as "grey" for most patients; this means that effectiveness cannot be assessed and that there is not enough medium- or high-quality evidence. A "grey" classification does not mean that the method is ineffective or harmful; the lowest classification, on the other hand, means that there is evidence of ineffectiveness.
What happens if my doctor recommends it and I do not accept?
According to the regulator in the United Kingdom, patients who fund their own treatment may prefer several standard cycles instead of unproven add-on practices. It is sensible to ask why the recommendation is made, what it would change in your situation and how the procedure is described in the document you will sign. You make the decision in an informed way, by talking with your doctor.
Is assisted hatching a separate intervention on me?
No. The procedure is applied to the outer shell of the embryo in the laboratory; it involves no separate intervention for you.
Has a clear benefit been shown for live birth?
No. A clear benefit could not be shown in the review. This does not mean that the ineffectiveness of the procedure has been proven; its benefit has not yet been shown.
Does a possible increase in clinical pregnancy mean a definite benefit?
No. The reliability of the small increase reported is low, and depending on the analysis method no difference or very little may be found. A clear benefit could not be shown for live birth.
Is the benefit certain in advanced age or repeated failure?
No. Although it has been put forward that it may be useful in these groups, there are not enough data. It is not possible to distinguish which group would benefit.
Is assisted hatching recommended for all IVF patients?
No. Current assessments do not recommend its routine use. You can ask your doctor why it is recommended for you and what evidence it rests on.
Is there a possibility of harm to the embryo?
Yes. Although no known additional procedure risk is stated for you, there is a possibility of harm to the embryo.
Is the link with identical twinning certain?
No. A concern has been reported on this subject; however, the number of cases is insufficient for a definite result and the studies contradict one another. The possibility of an increase in multiple pregnancy is also assessed separately.
Is assisted hatching the same as embryo biopsy?
No. Biopsy is the taking of cells from the embryo for genetic examination. The purpose of assisted hatching is different; you can clarify which procedure is planned.
Can an additional fee be requested for the procedure?
Yes. An additional fee may be involved. You can talk with your doctor about the reasoning for this practice, whose benefit has not yet been shown, its cost and its description in the consent document.
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