Freezing eggs or embryos lets you keep them for use in a later treatment cycle. Today most clinics use a fast-freezing method called vitrification. This page explains each step, what it feels like, and the limits you should know before deciding.
What it is
Cryopreservation means storing living cells at very low temperatures. In fertility care it can be used for unfertilised eggs (egg freezing) or for embryos made during IVF or ICSI (embryo freezing).
| Feature | Vitrification | Slow freezing |
|---|---|---|
| How it works | High-strength cryoprotectant, then plunged straight into liquid nitrogen | Less cryoprotectant, cooled gradually over about two hours |
| Ice crystals | Cells turn glass-like, avoiding ice crystals | Higher risk of ice damage |
| Survival after warming | Better for eggs and early embryos in a large review | Lower; now used less often |
A 2017 systematic review concluded that vitrification is the best strategy for all stages, from eggs to blastocysts.
| Compare | Egg freezing | Embryo freezing |
|---|---|---|
| What is frozen | Unfertilised eggs | Fertilised eggs (embryos) |
| Sperm needed now? | No | Yes |
| When it can be frozen | After egg collection | Cleavage stage (4 to 8 cells, about day 3) or blastocyst (200 to 300 cells, day 5 to 7) |
Who it's for
- People who want to keep eggs for later, for personal or medical reasons
- People about to start cancer treatment such as chemotherapy or radiation
- Couples in IVF who have good-quality embryos left after transfer
- Couples choosing to transfer one embryo and keep the others for later
Experts generally suggest freezing eggs before about age 38 for better chances, though this is not a strict cut-off.
Step by step
- Hormone injectionsDaily injections for about 10–12 days help several eggs mature, checked with blood tests and ultrasound scans.
- Egg collectionA short procedure, typically 15–30 minutes under light anaesthesia, removes mature eggs from the ovaries.
- Eggs or embryos are preparedEggs are checked and frozen the same day. For embryo freezing, eggs are first fertilised and grown in the lab.
- Cryoprotectant and vitrificationA protective solution works like antifreeze; then the cells are cooled extremely fast into a glass-like state.
- StorageStraws are kept in liquid nitrogen tanks at about −196 °C until needed.
- Warming and useEggs or embryos are warmed and the cryoprotectant removed. Thawed eggs are fertilised by ICSI; embryos are transferred to the womb.
Freezing makes the outer shell of an egg tougher, so sperm may not get in naturally. That is why thawed eggs are fertilised with ICSI.
Vitrification uses more cryoprotectant and plunges the cell straight into liquid nitrogen. Slow freezing cools it gradually over about two hours. HFEA notes that vitrification is more successful than slow cooling for eggs.
When needed, embryos are taken out of liquid nitrogen, warmed, soaked to remove the cryoprotectant, and transferred to the uterus. A frozen embryo keeps the biological age it had when it was frozen.
What it feels like
The injection phase means daily self-injections and several clinic visits for scans and blood tests. The whole egg freezing process takes about 2–3 weeks.
Egg collection is done under sedation or anaesthesia, so you should not feel the procedure. Some soreness or bruising afterwards is common. The freezing itself happens in the lab and involves nothing from you.
How to prepare
- Ask what your age and test results mean for your chances
- Ask how long storage lasts and how consent is renewed
- Keep your contact details up to date with the clinic
- Plan a day off for egg collection
- Don't assume frozen eggs guarantee a future pregnancy
- Don't drive yourself home after sedation
- Don't ignore severe bloating or pain during injections
- Freezing and thawing can damage eggs or embryos; if several are frozen, some or all may not survive.
- Stimulation can cause ovarian hyperstimulation syndrome (OHSS), which can be serious.
- The main risk is that treatment does not lead to a baby; success depends strongly on age at freezing.
Ask any clinic for age-specific results. HFEA suggests looking at fresh IVF figures too, as frozen-egg figures tend to be lower. In the UK, under-38s typically have around 7 to 14 eggs collected per cycle.
Storage rules differ by country. In the UK, since July 2022 eggs, sperm or embryos can be stored for up to 55 years, with consent renewed every 10 years. Check the consent forms for what happens when storage ends.
Risks and limits
| Risk | What it means |
|---|---|
| Ovarian hyperstimulation syndrome (OHSS) | Ovaries over-respond to hormone drugs; the main medical risk of the injection phase |
| Loss in freezing or warming | Not all eggs or embryos survive; very occasionally none do |
| No pregnancy | ASRM estimates one frozen egg has only about a 2–12% chance of becoming a baby |
| Multiple pregnancy | Higher if more than one embryo is transferred |
Storage rules differ by country. In the UK, for example, eggs and embryos can now be stored for up to 55 years, with consent renewed every 10 years.
How DBN does it
- Eggs and embryos are vitrified and stored at −196 °C
- Egg freezing involves about 2 weeks of injections
- Approximate price: 120,000–180,000 THB, plus 8,000 THB per year for storage
- In IVF, DBN transfers one embryo at a time to reduce twin risk
The first consultation is free, and prices are confirmed at consultation.
When to see a doctor
- You are thinking about freezing eggs and want to understand your chances
- You are about to start cancer treatment
- You have stored embryos and want to plan a frozen transfer
- You have severe bloating, pain or breathlessness during injections
Questions & answers
Is vitrification better than slow freezing?
A large review found better survival with vitrification for eggs and early embryos, and recommended it for all stages.
How long can eggs or embryos stay frozen?
Embryos can be stored for many years; ASRM notes live births from embryos frozen for nearly 30 years. Legal limits vary by country.
Do I need ICSI with frozen eggs?
Usually yes, because freezing toughens the egg's outer coating.
Related DBN services
Related articles
Sources
- Egg freezing — HFEA
- Embryo freezing — HFEA
- Embryo Freezing (Cryopreservation) — Cleveland Clinic
- Can I freeze my eggs to use later if I'm not sick? — ASRM ReproductiveFacts
- In Vitro Fertilization Treatment Journey — ASRM ReproductiveFacts
- Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification — Human Reproduction Update (2017)