In a frozen embryo transfer, an embryo frozen during an earlier IVF cycle is thawed and placed in the uterus. The lining of the uterus is prepared either with your natural cycle or with hormone medicines, and freezing and storage need your written consent.
What a frozen embryo transfer is
During IVF, there may be more good-quality embryos than are transferred straight away. These can be frozen and stored. In a frozen embryo transfer (often shortened to FET), one of these embryos is thawed and placed in the uterus in a later cycle.
Some clinics also freeze all embryos and transfer none in the same cycle as egg collection. This is called a "freeze-all" approach.
How embryos are frozen
Most clinics now use vitrification, a very fast freezing method. The embryo is placed in a special solution and cooled so quickly that damaging ice crystals do not have time to form. It is then stored in liquid nitrogen.
Not every embryo survives thawing, but with vitrification most do. Your clinic can tell you what to expect in its own laboratory.
Why embryos are frozen
There are several reasons:
- Extra embryos. Transferring one embryo at a time and freezing the rest lowers the risk of twins and gives further chances without another egg collection.
- Reducing OHSS risk. If the ovaries have over-responded to stimulation, delaying transfer can lower the risk of ovarian hyperstimulation syndrome becoming severe.
- The lining is not ready. Sometimes the lining of the uterus or hormone levels are not right for transfer in the stimulation cycle.
- Testing. If embryos are being tested before transfer, they are frozen while waiting for results.
- Health or timing reasons, such as illness, or treatment that needs to be done first.
Preparing the uterus
The lining of the uterus (endometrium) needs to be ready to receive the embryo. There are two main ways to prepare it.
| Natural cycle | Medicated (hormone) cycle | |
|---|---|---|
| Who it suits | People with regular ovulation | People with irregular or no ovulation, or when timing needs control |
| Medicines | Few or none; sometimes a trigger injection or progesterone | Oestrogen to build the lining, then progesterone |
| Monitoring | Scans and sometimes blood tests to track ovulation | Scans to check the lining before starting progesterone |
| Timing | Follows your own ovulation | Planned by the clinic |
Some clinics also use a "stimulated" cycle, with tablets to help ovulation. Your doctor will explain which approach they suggest and why. Research has not shown that one method suits everyone.
The transfer day
The embryo is thawed on the day of transfer or shortly before. The transfer itself is like a fresh IVF transfer: a thin, soft tube is passed through the cervix, usually guided by ultrasound, and the embryo is placed in the uterus. It takes a few minutes and does not usually need sedation. Some people feel mild cramping.
You can usually go home soon afterwards and carry on with normal light activity. A pregnancy test follows around two weeks later. If you are on hormone medicines, do not stop them unless the clinic tells you to.
Good to know. It is natural to worry that a frozen embryo is "weaker" than a fresh one. Vitrification is now a routine part of IVF, and frozen transfers are widely used. Ask your clinic how they grade and assess embryos after thawing.
Storage and consent
Freezing and storing embryos is a long-term decision. Before anything is frozen, you will be asked to sign consent forms. These usually cover how long embryos will be stored, the storage fees, and what should happen to them if you no longer need them, if you separate, or if one partner dies.
Under the ART (Regulation) Act, 2021, ART procedures in India need the written informed consent of the people involved. Read the forms carefully, ask questions, and keep copies. You can usually update your decisions later in writing.
Caution. Make sure the clinic, and any bank that stores embryos, is registered under the ART Act. You can look up a clinic with our ART registry check.
When to see a doctor
Contact your clinic if you have tummy pain, a fever, or bleeding after a transfer. Call 112 or go to the nearest hospital if you have severe tummy pain, heavy bleeding, pain in the shoulder tip, or you feel faint, as these can be signs of an ectopic pregnancy or another emergency. If you have embryos in storage and are unsure about your next step, you can talk it through in an online consultation.
Sources
This is general information, not medical advice. It can't account for your history. Please talk to a doctor about your own situation. Medical disclaimer
Severe pain, heavy bleeding or fainting? Call 112 or go to the nearest hospital.