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.
You may wish to consider freezing your embryos if:
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.
Before your embryos are frozen it’s very important you give your informed consent by signing the relevant consent forms. These will explain:
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.
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.
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).
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.