Embryo freezing (cryopreservation) freezes and stores fertilized eggs for later use. It’s often used with fertility treatments that create embryos, such as in vitro fertilization (IVF). It also can help people preserve fertility and get pregnant in the future. Examples include people facing cancer treatment or going through gender transition.
Embryo freezing, also called embryo cryopreservation, is a process to freeze and store embryos for later use. An embryo is an egg that has been fertilized by a sperm. This process is a way to help people with fertility and reproduction.
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Embryo freezing often occurs after people have treatments to try to get pregnant. Examples include in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).
These procedures fertilize eggs with sperm, and they sometimes create extra embryos. You may choose to freeze extra embryos and use them later if you:
Embryo freezing is also used for fertility preservation. For example, a woman or person designated female at birth (DFAB) with cancer might want to save fertilized eggs before starting chemotherapy or radiation therapy if that treatment could affect their ability to get pregnant. A transgender man (transitioning to male) also might freeze eggs or embryos before taking hormones for the transition or having gender affirmation surgery.
Embryo cryopreservation freezes a fertilized egg. Fertility programs also may offer egg freezing, which freezes unfertilized eggs.
The decision to freeze embryos is personal. Costs vary widely, and medical insurance may not cover fertility treatments. You’ll have to consider your goals, the costs, ethical issues, your partner’s preferences and other considerations.
Freezing can damage embryos. Thawing them later can also damage them. If multiple embryos are frozen, some or all may not survive the process.
Your healthcare provider will talk to you about whether your embryos are suitable for freezing, thawing and implantation.
Scientists don’t yet agree on whether pregnancy has a better chance with a fresh or frozen embryo. Researchers continue to study the issue.
You have to give your permission to freeze embryos. Your healthcare provider will give you consent forms to read and sign. The paperwork should provide details such as:
Your healthcare provider can also help you decide during which embryonic stage it’s best to freeze one or more embryos. The stages where freezing is possible include:
There are two methods to freeze embryos: vitrification and slow freezing.
In vitrification, fertility professionals:
Slow freezing has fallen out of favor, but some fertility specialists may still use it. In slow freezing, fertility professionals:
For either process, the embryos are:
Interestingly, the embryos remain the biologic age at which they are frozen. So if you freeze them at age 35 and come back to use them at age 50, the embryo hasn’t aged.
When frozen embryos are needed later, a fertility specialist will:
Embryo freezing can help people get pregnant later in life if they are facing current barriers, such as:
Embryo freezing doesn’t pose risks to resulting pregnancies, such as congenital disabilities or health problems. In fact, outcomes research of frozen-thawed embryos show lower rates of preterm birth, low birth weight, growth restriction and perinatal mortality.
The main risks associated with embryo cryopreservation are:
Frozen embryo transfer occurs when an embryo is thawed and implanted into a woman’s uterus. The process is often successful. But rates vary widely based on many factors, including:
Your healthcare provider will help you understand the factors that may affect your chances of success.
You or your partner can change your mind at any time during the process. If one of the two parents decides not to proceed with the process, the fertility specialist can’t legally continue.
If one parent decides not to proceed after the embryos are already frozen, the specialist might suggest a waiting period to be sure. Then the embryos will be taken out of storage and allowed to perish.
If you don’t use frozen embryos, you can:
A note from Cleveland Clinic
Embryo freezing, or cryopreservation, is a process that freezes and stores fertilized eggs for later use. It can help people preserve fertility and have options for pregnancy later in life. If you’re considering embryo cryopreservation, talk to your primary care provider, gynecologist or fertility specialist.
Last reviewed by a Cleveland Clinic medical professional on 02/17/2022.
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