Embryo Freezing
Embryo Freezing
During a fresh IVF or ICSI treatment cycle, it is not uncommon for more embryos to be created than we are permitted to transfer. The surplus of good quality embryos remaining can be cryopreserved (frozen) for use in a future treatment cycle. This opportunity only occurs in approximately a third of cycles as embryos must be of a high quality before they will have a chance of surviving the freezing and thawing process. Embryo freezing will be discussed with you on an individual basis.
Embryo freezing (cryopreservation) is a method of preserving the viability of embryos by carefully cooling them to very low temperatures (-196 C) using a rapid freezing process called vitrification. Cryopreserved embryos are preserved in liquid nitrogen for future use.
What are the benefits of embryo freezing?
The benefit of embryo freezing is that a good quality embryo is kept for use in a future frozen embryo transfer cycle. This means for example, that if a couple have a baby from an IVF or ICSI cycle and wish to have a sibling, they do not need to undergo the IVF (ovarian stimulation and egg collection) process all over again. Similarly, if the first cycle is unsuccessful they can opt to use the frozen embryo rather than going through IVF treatment cycle.Some couples will have several embryos frozen and therefore enough frozen embryos for more than one subsequent cycle.It is also a method of fertility preservation due to the fact that the embryo is frozen at a younger age when the woman’s egg, and resulting embryo quality, may be at its best.
Is embryo freezing for me?You may wish to consider freezing your embryos:If you want the option of using your embryos in the future without the need to have ovarian stimulation.If 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 frozen cycle.If you have a condition, or you 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).If you are at risk of injury or death (for example you are 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.If 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. The embryos will be frozen by 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:
What happens when embryos are frozen?Not all embryos are suitable for freezing so only good quality embryos will be chosen to freeze. The embryos will be frozen by 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?Frozen embryo transfer cycles are relatively simple. Most commonly, the woman takes hormone tablets to prepare the endometrium (lining of the womb). The process is monitored by transvaginal ultrasound scans to identify when the embryo transfer should take place.On the day of embryo transfer, the embryo is carefully thawed and reassessed for its quality. The process of transferring the embryo is similar to a smear test and does not require sedation. A fine catheter (tube) containing the embryo is carefully inserted into the uterus under ultrasound guidance. The embryo is then placed in the uterine cavity.Two weeks later a pregnancy test is performed.
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.
Does freezing damage the embryos?Not all embryos will survive the freezing and thawing process and very occasionally no embryos will survive. Approximately 80% of the embryos that are frozen will survive the thawing process. This does vary between patients and it’s possible that none of the embryos will survive the freezing and thawing process.It’s not uncommon for embryos that do survive to lose an occasional cell. 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, 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.
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?Frozen embryo transfer cycles are relatively simple. Most commonly, the woman takes hormone tablets to prepare the endometrium (lining of the womb). The process is monitored by transvaginal ultrasound scans to identify when the embryo transfer should take place.On the day of embryo transfer, the embryo is carefully thawed and reassessed for its quality. The process of transferring the embryo is similar to a smear test and does not require sedation. A fine catheter (tube) containing the embryo is carefully inserted into the uterus under ultrasound guidance. The embryo is then placed in the uterine cavity.Two weeks later a pregnancy test is performed.
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.
Does freezing damage the embryos?Not all embryos will survive the freezing and thawing process and very occasionally no embryos will survive. Approximately 80% of the embryos that are frozen will survive the thawing process. This does vary between patients and it’s possible that none of the embryos will survive the freezing and thawing process.It’s not uncommon for embryos that do survive to lose an occasional cell. 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, 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.
- 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.