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Laser Assisted Hatching

Patient information A-Z

Outside of the Cambridge IVF building
Five photos of embryos under a microscope and a photo of a baby

What is Assisted Hatching?

To successfully implant in the womb and form a pregnancy, the developing embryo must ‘hatch’ from its protective sheath (the Zona Pellucida). In some cases the zona pellucida can be thicker than normally expected or become hardened by procedures in the laboratory such as cryopreservation. Assisted hatching is a laboratory technique we use to introduce a weak spot into the zona pellucida to encourage the hatching process to occur naturally and at the right time.

At Cambridge IVF we use a technique called ‘Microsurgical Laser Assisted Hatching’ to perform this procedure using the latest in medical laser technology to ensure the process is as safe and effective as possible.

How Does the Process Work?

Once you have discussed the process with your consultant and agreed with them to proceed with assisted hatching you will need to indicate this on the relevant consent form which you will complete at your consultation. Following on from this, the laboratory team will be informed of your wishes and the process will be scheduled on the appropriate day (Day 3 for fresh treatment, Day 5/6 for frozen).

At the appropriate time a member of the lab team will first power up the laser and test it for precision and accuracy. Once this functional assessment has been performed they will remove the culture dish containing the embryos to be hatched from the incubator and transfer them into a dedicated dish for the hatching process. The dish is then loaded onto the micromanipulation microscope and the laser is targeted on the zona pellucida at a point furthest away from the cellular body of the embryo. The scientist will then perform a series of controlled ‘ablations’ on the zona pellucida and introduce the weak spot intended to assist the natural hatching process. This process usually takes between 3 and 5 controlled pulses of the laser (see image below).

Laser assisted treatment

The procedure only takes a matter of seconds and once it is completed the embryos or blastocysts are returned to their culture dish and replaced in the incubator.

Which embryos can we hatch?

We recommend hatching embryos before they form blastocysts in a fresh cycle as once the blastocyst has formed the zona pellucida is under pressure and any attempt to introduce a weak spot with the laser could result in damage to the cells and/or the embryo hatching prematurely. With this in mind if you have requested assisted hatching in your fresh treatment cycle we perform the procedure on the third day of development on all developing embryos.

For frozen blastocyst transfers it is possible to perform the hatching immediately after the blastocyst warming procedure whilst the blastocyst is still collapsed so we can safely hatch any blastocyst(s) prior to transfer on the day of your procedure.

What is the likelihood of embryos surviving the procedure?

The procedure is very straight forward and the microsurgical laser gives us precise control over the process. The chance of the laser making contact with any of the cells in the embryo is extremely low and our survival rate for the process is consistent at 100%.

What are the risks of using assisted hatching?

There is no conclusive evidence to suggest that assisted hatching brings with it any specific risk to you, the pregnancy or any children born as a result of treatment.

The laser itself generates heat but we control this by using a very low pulse duration and this heat is dissipated very quickly and is not detectable in the culture medium surrounding your embryo(s). We orientate the embryo to avoid the laser and any heat generated during its use having a direct effect on the cells of your embryo.

The main area of concern surrounds an increased risk of an identical twin pregnancy following the transfer of assisted hatched embryos. This may be due to the fact that by introducing the weak spot we somehow change the mechanism of hatching and this may result in a higher occurrence of the blastocyst breaking into to functional parts which then can both go on to form a viable foetus. The chances of this happening are very rare but in the interests of your health and safety we are very cautious about transferring more than one embryo which has undergone assisted hatching.

What does the HFEA say about assisted hatching?


According to the HFEA ‘Treatment Add On’ Traffic Light System, assisted hatching is rated red. This means that here is no evidence from high quality studies to support its use. Our own data suggests that there is some benefit for a small number of patients using frozen embryos where the zona pellucida (egg shell) is unusually thick. In these circumstances there may be a benefit to assisted hatching although this is unproven.

Is there a cost for Assisted Hatching?

Cambridge IVF do not charge an additional fee for Assisted Hatching where it is indicated or requested.

Comment on Witnessing

We are all very aware there have been IVF mix-ups in other clinics in the UK and across the world. Cambridge IVF has taken every step possible to minimise the risk of mix up occurring here. In addition to stringent checking and procedural controls being in place, we have invested in an electronic system called RI Witness which prevents the mixing of sperm and eggs from different patients or the transfer of the incorrect embryos in your cycle. We are not saying we are likely to have made a mistake without it, this could not be further from the truth but we do believe in making our processes as safe and risk free as possible and we believe that RI Witness ensures this.

We hope you have found this booklet informative and interesting. We realise we may not have covered all of your questions so if you do have any other queries we are here to help so please contact us via any of the means below:

Cambridge IVF
Kefford House
Maris Lane

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Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151