Frozen embryo transfer has overtaken fresh transfers in success rates worldwide. Discover why more clinics are recommending FET and how vitrification technology has transformed IVF outcomes.
The Shift from Fresh to Frozen
For decades, fresh embryo transfer was the standard in IVF. However, advances in vitrification have revolutionised the field. Today, frozen embryo transfer (FET) cycles often yield equal or higher pregnancy rates compared to fresh transfers, and most leading fertility centres worldwide now prefer the freeze-all approach.
What Is Vitrification?
Vitrification is a flash-freezing method that cools embryos so rapidly that ice crystals cannot form. This preserves the embryo's cellular structure with a survival rate exceeding 95-98% upon thawing. This breakthrough has made frozen embryo transfer a safe, reliable, and highly effective option.
Why FET Often Outperforms Fresh Transfers
- Better endometrial receptivity: After ovarian stimulation, elevated hormone levels can make the uterine lining less receptive. A FET cycle allows your body to return to its natural hormonal state, creating an optimal environment for implantation.
- Reduced risk of OHSS: Ovarian hyperstimulation syndrome (OHSS) is a serious complication of IVF. By freezing all embryos and delaying transfer, the risk of OHSS is significantly minimised.
- Time for genetic testing: Preimplantation genetic testing (PGT-A) requires several days to produce results. Freezing embryos allows time for comprehensive genetic screening before transfer.
- Flexibility in timing: FET gives patients and doctors the flexibility to choose the optimal transfer window rather than being constrained by the stimulation cycle timeline.
The FET Process: Step by Step
- Endometrial preparation: Your doctor will use oestrogen supplements to build the uterine lining to an ideal thickness of 8 mm or more.
- Progesterone supplementation: Once the lining is ready, progesterone is introduced to prepare the endometrium for implantation.
- Embryo thawing: On the day of transfer, your frozen embryo is carefully thawed in the laboratory. Survival rates with vitrification are excellent.
- Embryo transfer: A painless, ultrasound-guided procedure lasting about 10 minutes. No anaesthesia is required.
- Pregnancy test: A blood beta-hCG test is performed 12-14 days after the transfer.
Who Benefits Most from FET?
- Women at risk of OHSS (high AMH, PCOS, large number of follicles)
- Patients undergoing PGT-A for genetic screening
- Women with elevated progesterone on trigger day
- Patients who have surplus embryos from a previous cycle
- Those using donor eggs or embryos
FET Success Rates at Iswarya Fertility
At Iswarya Fertility, our FET success rates are among the highest in South India, thanks to our state-of-the-art embryology laboratory, experienced team of embryologists, and personalised protocols. We use time-lapse monitoring (EmbryoScope) and AI-assisted embryo grading to select the best embryo for transfer, maximising your chances of a healthy pregnancy.