Fertility treatments
Embryo freezing
Embryo freezing is an assisted reproduction technique that preserves fertilised eggs and can help people achieve pregnancy
What is embryo freezing?
Cryopreservation (freezing) of embryos is the process of preserving an embryo at sub-zero temperatures.
Often with in-vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) treatment, there may be some good quality embryos left after embryo transfer. Instead of disposing of 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 have a baby at a later date.
How does it work?
Firstly, you’ll need to be tested for any infectious diseases like HIV and hepatitis. 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 are put in a special solution containing substances (cryoprotectants), which help to draw water out from the embryo and provide protection in the cells. This protects them from damage caused by ice crystals forming. They’re then frozen, mostly by a technique called vitrification (fast freezing) and stored in tanks of liquid nitrogen until you’re ready to use them.
Does freezing damage the embryos?
Sadly, not all embryos will survive the freezing and thawing process and extremely rarely no embryos will survive.
It’s not uncommon for those embryos that do survive to lose a cell or two. In many cases the embryo will recover and continue to develop. Our clinic team will talk to you about whether the embryo is suitable to be transferred.
It’s just as safe and successful as using fresh embryos in treatment. The main risk is having a multiple birth (twins or triplets), which can pose 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.
Who is embryo freezing for?
You may wish to consider freezing your embryos if:
- You want the option of using your embryos in the future (rather than having a further fresh IVF or ICSI cycle).
- Your treatment needs to be cancelled after egg collection (for example, if you over respond to fertility drugs). You should be offered the opportunity to have any suitable embryos frozen to use later.
- You have a condition, or are facing medical treatment for a condition, that might affect your fertility. (fertility may be preserved either by storing eggs, embryos or a combination of both.)
- Your embryos are undergoing genetic testing due to a genetic condition running in the family or for other indications.
- 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.
