What frozen embryo transfer is
During an IVF cycle, there are often more good embryos than can be transferred at once. These can be frozen by vitrification, a very fast freezing method that protects the embryo.
In a later month, one embryo is thawed and transferred to the uterus. This is called a frozen embryo transfer, or FET. The woman does not need ovarian stimulation or egg collection again.
Why embryos are frozen
Freezing is not only for spare embryos. Sometimes the doctor plans to freeze all embryos and transfer later on purpose. Common reasons include:
- Extra good embryos after a fresh transfer, kept for a future pregnancy attempt
- Risk of OHSS: delaying transfer lets the ovaries settle after a strong response
- Lining not ready: a thin lining or high hormone levels during stimulation
- Fluid or polyps found in the uterus that need treatment first
- Genetic testing (PGT) of embryos, where results take time
- Personal or health reasons, such as illness or travel, that make a fresh transfer unwise
Our blog post on frozen vs fresh embryo transfer explains when each approach is chosen.
Natural and medicated FET cycles
The key to FET is timing. The embryo must be transferred when the lining of the uterus is ready to receive it. There are two main ways to prepare the lining.
| Point | Natural cycle FET | Medicated (hormone) FET |
|---|---|---|
| How the lining is prepared | By the woman's own ovulation | By estrogen, then progesterone |
| Best suited for | Women with regular cycles who ovulate on their own | Irregular cycles, PCOS, or no ovulation |
| Medicines | Few or none, sometimes progesterone support | Daily tablets, patches or gels for several weeks |
| Monitoring | More scans and sometimes blood tests to find ovulation | Fewer scans, easier to schedule |
| Flexibility of date | Depends on when ovulation happens | Transfer date can be planned in advance |
A modified natural cycle, using a trigger injection to time ovulation, is another option. The doctor chooses the method based on your cycle pattern, past response and travel needs.
The FET process, step by step
- ReviewThe doctor reviews your earlier cycle, the number and grade of frozen embryos, and any new reports.
- Baseline scanA scan early in the period confirms the ovaries and uterus are ready to start.
- Lining preparationEither your natural cycle is tracked, or estrogen is given to build the lining.
- Lining checkScans check the thickness and pattern of the lining.
- Progesterone startProgesterone begins on a set day so that the lining and the embryo stage match.
- ThawingOn transfer day, the embryologist thaws the embryo and checks that it has survived well.
- TransferThe embryo is placed in the uterus with a thin tube under ultrasound. No anaesthesia is needed.
- Pregnancy testA beta hCG blood test about two weeks later. Progesterone usually continues until then.
The whole FET cycle takes about three to five weeks from the start of the period to the pregnancy test.
Preparing for your FET
An FET cycle is lighter on the body than a fresh IVF cycle, but some preparation still helps. Start folic acid if you have stopped it, and keep thyroid and blood sugar well controlled.
Bring or share the embryology report from your IVF cycle. It shows how many embryos were frozen, their grade and the day they were frozen. This helps the doctor decide which embryo to thaw first.
- Take estrogen and progesterone exactly as prescribed, and do not stop without advice.
- Come for scans on the dates given, as the transfer day depends on them.
- Tell the doctor about any new medicine, illness or bleeding during the cycle.
If the lining does not grow well, the cycle may be paused and restarted. This is not a failure. Transferring into a poorly prepared lining would waste a good embryo, so waiting is usually the wiser choice.
What affects the result
Success with FET depends mainly on embryo quality, the woman's age when the embryos were made, and the health of the uterus. Sperm and egg quality matter because they shaped the embryo in the first place.
Survival after thawing is usually good with vitrification, but not every embryo survives. After reviewing your records, the doctor explains your realistic chances.
Risks to know about
FET avoids stimulation in that cycle, so the risk of OHSS is removed. The general risks of pregnancy remain, including ectopic pregnancy and miscarriage.
Transferring more than one embryo raises the chance of twins, which carries higher risk. We usually advise transferring one good embryo at a time.
Frozen embryos and the law
The ART (Regulation) Act, 2021 allows ART services to women above 21 and below 50. In May 2026 the Delhi High Court held that this limit applies when treatment starts. So a couple can continue with embryos frozen during treatment that began earlier. Consent for storage is signed by both partners.
FET cost in Delhi
An FET cycle at our clinic usually costs ₹40,000 – ₹80,000. This covers lining preparation, scans, thawing and the transfer, though the medicines depend on the method used.
If embryos are frozen during your IVF cycle, embryo freezing costs ₹15,000 – ₹40,000. Storage after that costs ₹5,000 – ₹15,000 per year.
You get a written, itemised estimate before the cycle starts. For the full picture of IVF charges, see our guide to IVF cost in India.
If your embryos are stored at another clinic, share the records on WhatsApp. The doctor can advise whether transferring them to our Delhi clinic is practical.