IVF Frozen Cycles vs Fresh Cycles

You told us you’d like to hear about the difference between frozen cycles IVF and IVF fresh cycles so hopefully the following information will be useful for you. You can also read our previous blog about IVF frozen embryo transfer vs fresh cycles here.

According to the latest HFEA Trends and Figures report published in May 2019, Frozen Embryo Transfer (FET) cycles have increased by 11% between 2016 and 2017 whilst the number of fresh embryo transfers has dropped by 2%. For the first time, Frozen Embryo Transfer cycles are now more successful than fresh (23 vs 22%) based on the HFEA’s national figures.

image of frozen embryo straws fresh vs frozen ivf

What are ‘fresh’ and ‘frozen’ IVF cycles?

Usually the following process is followed during an IVF ‘fresh’ cycle:

  • Patients take a range of medications for several weeks to stimulate egg production
  • The eggs are then collected during a short procedure and handed to the lab for fertilisation with the sperm
  • After 3 or 5 days the best quality embryo (or sometimes two) will be transferred back to the patient.
  • Freeze any remaining good quality embryos.

What does this mean in practice?

As an example, let’s say that a lady has received the stimulation drugs and gone through the egg collection procedure. She had nine eggs collected during the procedure and six of those successfully fertilised. One or perhaps two (if clinically advised) may be transferred back a few days after the procedure. These are classed as a ‘fresh’ transfer because the eggs have been ‘freshly’ collected recently.

Those of you who are good at maths can see there are then four or five successfully fertilised embryos left. This is when you can choose to have the remaining embryos frozen for use at a later stage.

Hopefully the fresh transfer you had would have been successful in creating a pregnancy but, if it wasn’t, you can then work your way through the frozen embryo transfer before you start your next fresh cycle.

In the case that the frozen embryo transfers (FETs) were unsuccessful, you would then undergo another ‘fresh’ stimulation and collection to get a new batch of eggs for fertilisation.

What is a ‘freeze-all’?

In some cases, the clinician may suggest a ‘freeze all’ where all the embryos created after egg freezing takes place and no embryo transferred in that cycle. This is usually suggested for patients who have over responded to drugs or have other issues where it may be beneficial for the womb lining (endometrium) to almost have a bit of a break before the transfer. This can help to make sure the endometrium is in the best condition for implantation, and therefore success.

It’s not a ‘one size fits all’ with anything to do with fertility and data suggests that a freeze-all policy should be individualised, presumably in favour of PCOS/hyper-responding patients. You can read more about the freeze all in our previous blog here.

Why have Frozen Embryo Transfer cycles seen such an increase?

Andrew Thomson, the Laboratory Manager at one of our partner clinics, the London Women’s Clinic, explains: using the latest vitrification (freezing) technology, embryos don’t deteriorate once frozen they are preserved at the age you are at the time of freezing. For example, if you were aged 35 when you froze the embryos, if you use them 5 years later, the embryos will still be 35! This means that today embryos can be thawed out and replaced in a Frozen Embryo Transfer (FET) cycle, when the patient is ready, with the same or better chance of success than in a fresh cycle.

Over the last few years, the scientific community have found that embryo transfer in a IVF frozen cycle may produce better results.  Due to the stimulation medication a patient is given prior to egg collection and the trauma of the egg collection procedure itself, an embryo transfer during this same cycle may not be the best or safest time.  It could also reduce the chance of pregnancy.  More clinics are opting to freeze the embryos and replace them in a FET cycle a month later or when the patient is ready.

A FET cycle uses minimal or no medication so one embryo can be replaced into a much more natural environment resulting in potentially higher success rates and hopefully a safer pregnancy. There has been a lot of research on this topic but at present there is still no consensus as to the best policy with different clinics favouring fresh or frozen embryos. Read the full LWC article here.

Frozen embryos don’t always survive the thawing process

Patients should be aware that there is a very small chance the embryos will not survive the freezing and thaw process.  In these instances, either another embryo will be thawed (if available) or the embryo transfer will be cancelled.

image of frozen IVF straws in liquid nitrogen storage canister fresh vs frozen ivf

When can I use frozen embryos?

Often with IVF treatment, there may be good quality embryos left over after embryo transfer. Instead of discarding them, there is the option to freeze them to use in the future (in case treatment doesn’t work for example, or to try for a sibling).

Embryos can also be frozen to preserve fertility so it may be possible to freeze embryos when you are 35 to have a baby at a later date as your embryos will still be the age they were at the time of freezing.

Are embryos affected by the length of time they’re frozen?

The standard storage period for embryos is normally 10 years for frozen embryos but this can be shorter or longer, depending on your circumstances. There has been no evidence to show any damage to embryos caused by the freezing process, or for the length of time they are in storage.

However, as mentioned earlier, there can be issues with some embryos not surviving the thawing process but this is not usually due to the length of time they have been in storage.

What are the success rates for Frozen Embryo Transfers

Success rates for IVF using frozen embryos have been increasing year on year and are now comparable to rates using fresh embryos. For women aged under 35, birth rates are slightly higher for fresh transfers and rates are level for women aged between 35-37. For women aged over 37, birth rates for frozen transfers have actually exceeded the rates for fresh embryos. This may be because the embryos transferred in the IVF frozen cycle were created using eggs collected some time ago, when the woman was younger.

image of cold and warm thermometer temperature fresh versus frozen ivf

Which option should I choose?

It’s not one size fits all and your clinician will advise what is best for your specific situation.

How much do IVF frozen cycles cost?

It can cost, on average, between £800 and £1500 for thawing and transferring an embryo to the womb.

Please note that, depending on where you live, you may not be able to have embryo freezing on the NHS.

You can be reassured though that if you have to go privately for your treatment and you have an Access Fertility programme you are covered for up to 3 fresh cycles and unlimited FETs. You also get one year freezing and storage included with these packages.

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