Frozen Embryo Transfer (FET)
Frozen embryo transfer (FET) is an IVF procedure in which previously cryopreserved embryos are thawed and transferred into the uterus during an optimally prepared cycle.
FET allows separation of ovarian stimulation from transfer, reduces risks associated with fresh cycles (like OHSS), and provides the flexibility to time transfer for the best endometrial receptivity.
Modern vitrification preserves embryo viability very effectively so pregnancy rates from FET are comparable to fresh transfers in many settings.
Overview And Clinical Background
Why freeze and transfer later
FET became routine with advances in vitrification that deliver high post-thaw survival and comparable implantation rates to fresh embryos.
It is used after freeze-all strategies, for embryos saved from prior cycles, or to delay transfer for medical or personal reasons.
FET supports single-embryo transfer policies and allows preimplantation genetic testing results to be available prior to transfer.
- Advantages: Flexibility of timing, reduced ovarian stimulation risks, and often improved endometrial synchrony compared with some fresh cycles.
- Enables elective single embryo transfer and staged approaches to fertility care.
- Common use: After freeze-all cycles due to high ovarian response, for PGT-tested embryos, or when delaying pregnancy is preferred.
Symptoms, Signs And Presentation
Patients seeking FET include those with vitrified embryos from prior IVF cycles, individuals using donor embryos, or couples opting to delay implantation.
Presentation centers around planning the optimal endometrial preparation method to maximise implantation probability.
- Typical candidates: Patients with frozen embryos, those who underwent PGT, or individuals needing cycle timing flexibility.
- Women with prior fresh-cycle complications may prefer FET for safety and improved uterine conditions.
- Consideration: Endometrial receptivity and hormonal milieu are the main determinants of FET success.
Diagnosis Methods And Investigations
Preparing the uterus and assessing embryo quality
Pre-transfer workup includes hormonal profiling, ultrasound assessment of endometrial thickness and possibly an endometrial receptivity test in recurrent implantation failure.
The thawed embryo is examined for survival and morphological integrity before transfer.
- Pre-transfer tests: Serum estradiol/progesterone, ultrasound for endometrial pattern and thickness, and infectious screening as required.
- Embryo check: Post-thaw viability assessment ensures the embryo appears structurally intact and suitable for transfer.
- Optional tests: ERA (endometrial receptivity assay) or timed progesterone monitoring for personalized transfer timing.
Treatment Options And Surgical Techniques
Endometrial preparation can be natural, modified natural, or artificially hormonally prepared depending on ovulation status and clinic protocol.
Transfer is performed under ultrasound guidance with a soft catheter; luteal support with progesterone continues until the pregnancy test and beyond if positive.
- Natural cycle FET: Best for ovulatory patients—monitoring for natural ovulation and timed transfer without exogenous hormones.
- Hormone replacement FET: Estradiol and progesterone prepare the lining when natural cycles are irregular or suppressed.
- Transfer technique: atraumatic ultrasound-guided catheter placement and brief post-transfer rest to optimise embryo apposition.
Recovery, Risks And Prognosis
FET is outpatient with quick recovery and minimal discomfort.
Pregnancy rates per transfer are high with modern cryopreservation; risks mirror IVF generally, including multiple pregnancy if more than one embryo is transferred and early pregnancy loss.
Overall, FET often demonstrates stable, reproducible outcomes across cycles.
Why Choose Us
CureU Healthcare provides accredited cryostorage, meticulous thaw protocols and personalised endometrial preparation to maximise FET success.
Our team coordinates timing, monitors hormonal status closely and supports patients with evidence-based luteal support and counselling.
Conclusion
Frozen embryo transfer offers safe, flexible and effective embryo implantation with outcomes comparable to fresh transfers when protocols are individualised.
With careful uterine preparation and expert embryology, FET is a central tool in modern assisted reproductive care.
