Assisted hatching is a specialised laboratory technique that may be used as part of an in vitro fertilisation (IVF) treatment. The procedure involves creating a very small opening or thinning an area of the zona pellucida, the protective outer layer surrounding the developing embryo.
Before implantation can occur, an embryo must naturally “hatch” from this outer shell so that it can interact with and attach to the lining of the uterus. Assisted hatching is designed to facilitate this process and is usually performed by an experienced embryologist using highly precise laboratory techniques, most commonly laser technology.
The procedure is not required in every IVF cycle. It may be considered in selected cases depending on factors such as the patient’s reproductive history, previous IVF outcomes and the characteristics of the embryos observed in the laboratory.
Although assisted hatching has been proposed as a way of supporting embryo implantation, current scientific evidence does not demonstrate that it routinely increases live birth rates for all patients undergoing IVF. For this reason, the decision to use assisted hatching should be individualised and discussed with the fertility specialist and embryology team.
cycles, while evidence regarding potential benefits for specific groups of patients remains limited. Therefore, its use should be evaluated individually by the fertility specialist and embryology team.
How Is Assisted Hatching Performed?
Assisted hatching is performed in the embryology laboratory by a specially trained embryologist. It is a microscopic procedure carried out on the embryo before embryo transfer and does not require any additional intervention or anaesthesia for the patient.
The procedure generally includes the following steps:
1. Embryo Assessment
Before assisted hatching is performed, the embryologist evaluates the developing embryo and the zona pellucida, the outer protective layer surrounding it. The stage and morphology of the embryo, as well as the treatment plan, are taken into consideration.
2. Positioning the Embryo
The embryo is placed under a specialised microscope and carefully stabilised using micromanipulation equipment. This allows the embryologist to work with very high precision while avoiding the cells of the embryo.
3. Creating an Opening in the Zona Pellucida
A very small area of the zona pellucida is thinned or opened. Different techniques have been used for assisted hatching, including mechanical and chemical methods, but laser-assisted hatching is commonly used in modern IVF laboratories.
With laser-assisted hatching, controlled laser pulses are directed at a selected part of the zona pellucida. This enables the embryologist to create a precise opening while limiting manipulation of the embryo.
4. Embryo Transfer
Following the procedure, the embryo continues to be handled according to the IVF treatment plan and may then be prepared for transfer into the uterus.
The purpose of assisted hatching is to facilitate the embryo’s natural hatching from the zona pellucida before implantation. However, assisted hatching remains an additional IVF laboratory technique rather than a routine requirement for every patient. Current evidence has not demonstrated a significant improvement in live birth rates when laser-assisted hatching is routinely performed in all IVF patients.
Who May Be Considered for Assisted Hatching?
Assisted hatching is not routinely recommended for every patient undergoing IVF. Instead, it may be discussed in selected cases after evaluation of the patient’s reproductive history, previous IVF outcomes and the characteristics of the embryos in the laboratory.
Situations in which assisted hatching has historically been considered include:
Advanced Maternal Age
Assisted hatching has sometimes been proposed for women of advanced reproductive age, as changes in the characteristics of the zona pellucida have been suggested as one possible factor affecting the natural hatching process.
However, current evidence does not clearly demonstrate that assisted hatching improves live birth rates specifically on the basis of maternal age alone.
Previous Unsuccessful IVF Attempts
The technique may also be discussed in patients who have experienced repeated unsuccessful IVF or embryo transfer attempts, particularly when good-quality embryos have previously been transferred without resulting in pregnancy.
Nevertheless, implantation failure can have many different causes, and assisted hatching cannot address all of them. A broader evaluation may therefore be required before another IVF attempt.
Specific Characteristics of the Zona Pellucida
During embryo assessment, the embryologist may observe particular characteristics of the zona pellucida, such as increased thickness or other features that could theoretically make natural hatching more difficult.
In selected circumstances, the embryology team may consider whether assisted hatching could be appropriate.
Selected Frozen Embryo Transfer Cycles
Assisted hatching has also been studied in frozen embryo transfer (FET) cycles. However, available evidence remains insufficient to establish that routinely performing laser-assisted hatching improves live birth rates in these cycles.
For this reason, the decision should always be individualised rather than automatically included in an IVF protocol.
Overall, factors such as age over 35, previous IVF failures, elevated FSH or a thicker zona pellucida should not automatically be considered indications for assisted hatching. According to the ASRM, there is currently insufficient evidence to recommend the technique routinely even for patients considered to have a poorer IVF prognosis.
Similarly, the HFEA currently rates assisted hatching as having insufficient moderate- or high-quality evidence to determine whether it increases the chance of having a baby for most fertility patients.
Potential Advantages of Assisted Hatching in IVF
The main purpose of assisted hatching is to facilitate the embryo’s natural ability to emerge from the zona pellucida before implantation. Although the technique has theoretical advantages, its potential benefits should be considered on an individual basis.
Supporting the Natural Hatching Process
Before an embryo can implant in the uterus, it must hatch from the zona pellucida. Assisted hatching creates or thins a small area of this outer layer, potentially making it easier for the developing blastocyst to complete this natural process.
Precise Embryo Manipulation
When laser-assisted hatching is used, the embryologist can target a very small and specific area of the zona pellucida. The laser allows controlled manipulation without extensive mechanical handling of the embryo.
Possible Role in Selected IVF Cases
Assisted hatching may be considered in selected IVF cases after assessment of the patient’s reproductive history and embryo characteristics. For example, it has been investigated in patients with previous unsuccessful IVF attempts, poorer prognosis or frozen embryo transfer cycles.
However, current evidence is insufficient to confirm that these groups consistently benefit from the procedure.
Additional Laboratory Option
Assisted hatching provides the fertility team with an additional embryology technique that may be incorporated into an individualised IVF treatment plan when there is a specific reason to consider it.
It is important to understand that these potential advantages do not mean that assisted hatching increases IVF success rates for every patient. The American Society for Reproductive Medicine states that laser-assisted hatching should not be routinely recommended for all IVF patients, while current evidence does not demonstrate a significant improvement in live birth rates in fresh IVF cycles.
For this reason, the potential value of assisted hatching should always be evaluated in relation to the individual patient and the overall IVF treatment plan.
Does Assisted Hatching Improve IVF Success Rates?
Whether assisted hatching improves IVF success rates remains an area of scientific debate. Although the technique is designed to facilitate the embryo’s emergence from the zona pellucida before implantation, this theoretical advantage has not consistently translated into higher live birth rates.
Some studies have reported improvements in implantation or clinical pregnancy rates in particular groups of patients. However, when the most important IVF outcome — the live birth rate — is considered, the evidence is less convincing.
According to the American Society for Reproductive Medicine (ASRM), there is moderate evidence that assisted hatching does not significantly improve live birth rates in fresh IVF cycles. For patients considered to have a poor prognosis, including those with previous unsuccessful IVF attempts, the available evidence is mixed and insufficient to recommend assisted hatching routinely. Evidence is also insufficient to support its routine use in frozen embryo transfer cycles.
The UK Human Fertilisation and Embryology Authority (HFEA) currently gives assisted hatching a grey rating, meaning there is insufficient moderate- or high-quality evidence to determine whether the technique increases the chance of having a baby for most fertility patients.
For this reason, assisted hatching should not be viewed as a procedure that automatically increases the likelihood of IVF success. Its potential use should instead be considered individually, taking into account the patient’s reproductive history, embryo characteristics and the recommendations of the fertility specialist and embryology team.
Ultimately, IVF success depends on multiple factors, including maternal age, embryo quality, chromosomal competence, endometrial factors and the underlying cause of infertility. Assisted hatching represents only one possible laboratory intervention within a much broader treatment strategy.
Are There Any Risks or Limitations of Assisted Hatching?
Assisted hatching is a laboratory procedure and does not require any additional medication, surgery or anaesthesia for the patient. However, because it involves direct manipulation of the embryo and the zona pellucida, there are certain risks and limitations that should be considered.
Possible Damage to the Embryo
One of the main potential risks is accidental damage to the embryo or to individual embryonic cells during manipulation of the zona pellucida. Modern laser systems allow the embryologist to work with a high degree of precision, but no micromanipulation procedure is completely without risk.
For this reason, assisted hatching should be performed by an experienced embryology team using appropriate laboratory equipment.
Possible Association With Identical Twinning
Some studies have suggested that manipulation of the zona pellucida may be associated with an increased likelihood of monozygotic, or identical, twins.
However, the evidence is conflicting. Some studies have reported an association, while others have not demonstrated an increased risk. Current evidence is therefore insufficient to confirm that assisted hatching itself causes a higher rate of monozygotic twinning.
No Guaranteed Improvement in IVF Success
Perhaps the most important limitation is that assisted hatching does not guarantee embryo implantation or pregnancy.
Implantation is a complex biological process influenced by many factors, including embryo quality, chromosomal status, maternal age, endometrial receptivity and the underlying causes of infertility.
Current scientific evidence does not demonstrate that routine assisted hatching significantly improves live birth rates for all IVF patients.
Not Necessary in Every IVF Cycle
Assisted hatching should therefore be regarded as an additional laboratory technique rather than a standard requirement of IVF. Its potential use should be considered individually by the fertility specialist and embryologist based on the characteristics of each treatment cycle.
Patients considering assisted hatching should discuss its potential benefits, limitations and any additional costs with their fertility team before deciding whether the technique is appropriate for their IVF treatment.
Assisted Hatching and Embryo Transfer
Assisted hatching is performed in the embryology laboratory as part of the management of the embryo and, when used to support implantation, takes place before the embryo is transferred into the uterus.
Before implantation can occur, a developing blastocyst must naturally emerge from the zona pellucida. Assisted hatching creates or thins a small area of this protective layer with the aim of facilitating that process.
Once the laboratory procedure has been completed, the embryo is managed according to the planned IVF protocol and can subsequently be transferred into the uterus.
Does Assisted Hatching Change the Embryo Transfer Procedure?
For the patient, the embryo transfer itself is generally performed in the same way whether assisted hatching has been used or not.
The selected embryo is placed into the uterine cavity through a thin embryo transfer catheter. Assisted hatching does not require an additional surgical procedure, medication or anaesthesia for the woman.
The main difference occurs before the embryo transfer in the IVF laboratory, where the embryologist performs the microscopic manipulation of the zona pellucida.
Does Assisted Hatching Guarantee Implantation?
No. Creating an opening in the zona pellucida does not mean that the embryo will necessarily implant.
Successful implantation involves a complex interaction between the embryo and the endometrium and can be influenced by factors such as embryo competence, maternal age, uterine and endometrial factors and the underlying cause of infertility.
Although assisted hatching is intended to facilitate one stage of the implantation process, current evidence does not show that routinely adding it to IVF significantly improves live birth rates. For this reason, it should not be considered a standard requirement before every embryo transfer.
The decision to perform assisted hatching should therefore form part of an individualised IVF treatment plan after discussion between the fertility specialist, embryology team and patient.
Assisted Hatching at Our Fertility Clinic
At our fertility clinic, assisted hatching is considered on an individual basis as part of a personalised IVF treatment plan. It is not automatically recommended for every patient or every embryo transfer.
Before deciding whether assisted hatching may be appropriate, the fertility specialist and embryology team evaluate factors such as:
- the patient’s age and reproductive history,
- previous IVF and embryo transfer outcomes,
- the characteristics and developmental stage of the embryos,
- the appearance of the zona pellucida,
- and the overall IVF treatment strategy.
When assisted hatching is selected, the procedure is performed in the embryology laboratory using precise micromanipulation techniques. The objective is to modify a very small area of the zona pellucida while minimising unnecessary manipulation of the embryo.
An Individualised Approach to IVF
Every IVF cycle is different. A technique that may be considered in one case may provide no additional benefit in another. For this reason, Dr Panagiotis Kaliantzis and the fertility team assess each patient individually before recommending additional laboratory procedures such as assisted hatching.
Patients are informed about the purpose of the technique, the available scientific evidence, its potential limitations and whether there is a specific reason to consider it in their treatment.
The aim is not to add procedures unnecessarily, but to develop an IVF strategy based on each patient’s medical history, fertility assessment and embryo development.
Patients who are preparing for IVF or who have experienced previous unsuccessful embryo transfers can discuss with their fertility specialist whether assisted hatching may have a role in their individual treatment plan.
Frequently Asked Questions About Assisted Hatching
What is assisted hatching in IVF?
Assisted hatching is a laboratory technique used during IVF in which an embryologist creates or thins a very small area of the zona pellucida, the protective outer layer surrounding the embryo. The aim is to facilitate the embryo’s natural hatching process before implantation.
Is assisted hatching necessary for every IVF cycle?
No. Assisted hatching is not considered a routine requirement for every IVF patient. Current evidence does not show that it consistently improves the chance of having a baby when used routinely, so its use should be assessed individually.
Who may be considered for assisted hatching?
The procedure may be discussed in selected cases, such as patients with previous unsuccessful IVF attempts or particular embryo characteristics. Maternal age, reproductive history and laboratory findings may also be considered. However, there is currently no high-quality evidence demonstrating a clear benefit for any specific group of patients.
Does assisted hatching improve implantation?
Assisted hatching is designed to facilitate the embryo’s emergence from the zona pellucida, which is necessary before implantation can occur. Some studies have reported improvements in certain intermediate outcomes, but evidence does not clearly demonstrate that routine assisted hatching increases live birth rates.
Is laser-assisted hatching safe?
Laser-assisted hatching allows the embryologist to precisely target a small area of the zona pellucida. However, because the technique involves direct manipulation of the embryo, there is a small possibility of accidental damage. It should therefore be performed by an appropriately trained embryology team.
Is assisted hatching painful?
No. Assisted hatching is performed directly on the embryo in the IVF laboratory. The patient does not undergo an additional surgical procedure and does not require anaesthesia specifically for assisted hatching.
When is assisted hatching performed?
When used in relation to embryo transfer, assisted hatching is performed in the embryology laboratory before the embryo is transferred into the uterus. The precise timing depends on the embryo’s developmental stage and the IVF treatment plan.
Can assisted hatching guarantee successful implantation?
No. Assisted hatching cannot guarantee implantation or pregnancy. IVF success depends on several factors, including embryo competence, maternal age, chromosomal factors, endometrial conditions and the underlying cause of infertility.
Is assisted hatching recommended after failed IVF?
A previous unsuccessful IVF or embryo transfer may lead the fertility team to review whether additional laboratory techniques could be considered. However, assisted hatching is not automatically recommended after a failed IVF attempt. Repeated implantation failure may have several possible causes and should be evaluated individually.
Should I choose assisted hatching for my IVF treatment?
The decision should be made after discussion with your fertility specialist and embryology team. They can assess your previous treatment history, embryo characteristics and overall IVF plan and explain whether there is a specific reason to consider assisted hatching in your case.
