Embryo freezing

Often with IVF or ICSI treatment, people have good quality embryos leftover which they can’t use. Instead of discarding them, they have the option to freeze them to use in the future (in case treatment doesn’t work for example, or they want to try for a sibling).

If you’re having medical treatment that would damage your fertility, such as radiotherapy or chemotherapy, or you have a progressive condition that could affect your fertility in the future, you may want to create embryos with your partner to freeze. If you do this, it’s important to be aware that you or your partner can change your minds at any time about using the embryos in treatment.

CRGW have an excellent embryo freezing program where over 98% of embryos frozen survive being thawed.

Is embryo freezing for me?

You may wish to consider freezing your embryos if:

  • You want the option of using your embryos in future IVF or ICSI cycles.
  • Your treatment needs to be cancelled after egg collection (for example, if you have a bad reaction to fertility drugs). You should be offered the opportunity to have any suitable embryos frozen to use in a later cycle.
  • You have a condition, or are facing medical treatment for a condition, that might affect your fertility (embryo freezing is currently the most effective way for women to preserve their fertility).
  • You are at risk of injury or death (for example you’re a member of the Armed Forces who is being deployed to a war zone) and you want to create and freeze embryos with your partner.
  • You are due to undergo a sex change operation and you want to create and freeze embryos with your partner.

What happens when embryos are frozen?

Not all embryos are suitable for freezing so only good quality embryos will be chosen to freeze. Embryos can be frozen at different stages of their development – when they’re just a single cell, at the two to eight cell stage or later in their development (called the blastocyst stage).

The embryos will be put in a special substance, which replaces water in their cells. This will protect the embryos from damage caused by ice crystals forming. They’ll then be frozen, either by cooling them slowly or fast freezing (vitrification) and stored in tanks of liquid nitrogen until you’re ready to use them.

How much control do I have over what happens to my embryos?

Before your embryos are frozen it’s very important you give your informed consent by signing the relevant consent forms. These will explain:

  • How long you want the embryos to be stored for.
  • What should happen to your embryos if you or your partner were to die or become unable to make decisions for yourself.
  • Whether the embryos are to be used for your own treatment only, or whether they can be donated for someone else’s treatment, or used for research.
  • Any other conditions you may have for the use of your embryos.

How long can my embryos be stored for?

The standard storage period for embryos is normally 10 years although women in certain circumstances can store their embryos for up to 55 years. Your clinician will be able to explain whether you can do this.

You must let the clinic know if you change address. This is particularly important if you have decided to store your embryos for less than 10 years as if the clinic can’t reach you, they may have to take your embryos out of storage and allow them to perish.

If you have the option to store for 55 years, you’ll need to confirm that you want to continue storing your embryos and your doctor will need to confirm that you’re eligible to do so. Again, it’s vital that you stay in touch with your clinic to prevent your embryos from being discarded if your storage runs out.

What if one of us changes our mind about using or donating them?

You, your partner or the donor(s) (if applicable) can vary or withdraw consent at any time before the embryos are used in treatment or research. If your partner withdraws their consent then your embryos cannot be used in treatment.

If one person withdraws consent (either the person who provided the eggs or the sperm) then there will be a ‘cooling-off’ period of up to a year, which will allow you to decide what should happen to the embryos. If after this time your partner still doesn’t want the embryos to be used, they’ll be removed from storage and allowed to perish.

What happens when I want to use them?

The initial steps depend on whether you are ovulating regularly. If your periods are regular your doctor may suggest having the embryo transferred to your womb with no fertility drugs. In this case, ultrasound scans may be used to check the lining of your uterus. Urine or blood tests may be used to check when you’re ovulating (releasing an egg), which indicates that the lining of your womb will be ready to receive the embryo.

If your periods aren’t regular, or you don’t have them at all, your doctor may suggest using drugs to suppress your natural cycle and trigger a ‘false’ period. You are then given medication to help prepare the uterus lining for an embryo.

When the timing’s right, the clinic’s embryologist (embryo specialist) will thaw your embryos and usually transfer one embryo to your womb (three embryos can be transferred in exceptional circumstances if you’re over 40).

How successful is embryo freezing?

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 frozen cycle were created using eggs collected some time ago, when the woman was younger.

Does freezing damage the embryos?

Sadly, not all embryos will survive the freezing and thawing process and very occasionally no embryos will survive. At CRGW as we have over 98% survival for embryo freezing and thawing the failure of an embryo to survive is incredibly rare.

It’s not uncommon for embryos that do survive to lose an occasional cell (the cell breaks or ‘lyses’). In many cases the embryo will recover and replace those cells but if they don’t then those embryos may not be transferred.

How safe is it to use frozen embryos in treatment?

It’s just as safe as using fresh embryos in treatment. The main risk is having a multiple birth (twins or triplets), which can pose serious health risks to both mum and babies. You can reduce your risk of having a multiple birth by transferring only one embryo to the womb, a process known as elective single embryo transfer or eSET.

What if I don’t use my embryos or I have some left over?

You can either discard them or donate them. In both cases, you and your partner/donor will need to give your consent in writing, ideally at the time your embryos are frozen. Your clinic should provide the relevant forms.  

Donate them to someone else: Give someone the most precious gift of all by donating your embryos to someone in need. 

Donate them to research: Research on eggs, sperm and embryos is invaluable in helping scientists to understand causes of infertility and develop new treatments.

Donate them to training: Trainee embryologists need embryos to practice techniques, such as removing cells from embryos and mastering the freezing/thawing process.

Discard them: Some people prefer to discard their embryos. Embryos that are no longer needed are simply removed from the freezer and allowed to perish naturally in warmer temperatures or water.