Vitrification (freezing)

What is vitrification?

We use a process called ‘vitrification’ to freeze sperm, eggs and embryos.

Vitrification involves much more rapid cooling than other less advanced methods of freezing, and it prevents ice crystals from forming.

This preserves the quality of the cells and improves the chances of surviving when they are thawed, compared to slow-freezing.

Embryo vitrification

Embryo vitrification is now a well-established procedure.

It allows us to freeze any good quality embryos that remain after embryo transfer or if transfer needs to be delayed.

Embryos can be frozen at various stages, depending on how they develop.

Whether embryos are frozen depends on:

• Your wishes, including whether you may want to repeat fertility treatment in the future

• Whether there are any spare good-quality embryos left after treatment

Vitrification is one of several techniques that have improved the outcomes of embryo freezing.

The most recent data from HFEA across all ages suggest frozen embryo transfers today have similar success rates to fresh embryo transfers.

Occasionally, it may be decided to vitrify all the embryos in a cycle and postpone embryo transfer.

The embryos can be thawed and used in a subsequent cycle.

We do this to help prevent ovarian hyperstimulation syndrome (OHSS) by avoiding repeated full IVF cycles.

Egg vitrification

We can use vitrification to successfully freeze eggs immediately after the collection procedure.

This is important for women who would like to store eggs before undergoing chemo- or radiotherapy, or other treatments that might affect their fertility in the future.

We also store eggs for women who are not ready to start a family now, but who may want to try fertility treatment to have a family in the future.

Usually, eggs collected and stored earlier in life are of a better quality than those women produce later on.

Patients who choose to freeze eggs when they are under 35 tend to have higher success rates.

It’s important to know that freezing your eggs doesn’t guarantee a successful pregnancy in the future.

But it does mean that future fertility treatment is an option.

This might be the right choice for you if you aren’t able to start a family now, whether that’s for personal or medical reasons.

Sperm freezing

You may need to store sperm for fertility preservation before certain medical procedures or in the course of a fertility treatment cycle.

This could be before:

• Having chemo- or radiotherapy

• Having a vasectomy

• Surgery that may result in impaired fertility

• A future fertility treatment using surgically retrieved sperm

• A future fertility treatment cycle, so you’ll have a ‘back-up’ sample for the day of treatment

Sperm that is donated for other couples or individuals to use also has to be vitrified and quarantined while all the appropriate donor screening tests are conducted.

The sperm is not released for use until all test results come back and are clear.

Should I consider eggs, sperm or embryo freezing?

It’s important to know that freezing your sperm, eggs or embryos doesn’t guarantee a pregnancy in the future.

But it does give the option to try fertility treatment at a time that’s right for you.

If you’re already having fertility treatment, then freezing your eggs, sperm or embryos can also give you the option to keep trying in future.

Before you choose to freeze your samples, your doctor should explain how it could benefit you, and how delaying starting a family could affect your chances of success.

That way, you can make an informed choice going forward.