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Embryo thawing is a routine part of modern IVF that prepares a frozen embryo for transfer. It is used whether an embryo is transferred to an intended parent or a gestational surrogate as part of a surrogacy journey.
Advances in vitrification have made it possible for most frozen embryos to survive the warming process, helping frozen embryo transfer (FET) become a standard approach in fertility treatment. Understanding what happens during thawing can help you know what to expect as you prepare for transfer and your next step toward growing your family.
How Does the Embryo Thawing Process Work?
Embryo thawing is a carefully controlled laboratory process that prepares a frozen embryo for transfer. An embryologist manages each step to safely warm and evaluate the embryo.
- Step 1: Retrieved From Storage: The embryo is removed from liquid nitrogen storage.
- Step 2: Warmed: It is placed in a specialized warming solution and gradually brought to the appropriate temperature.
- Step 3: Rehydrated: The cryoprotectants used during freezing are removed and replaced with fluid.
- Step 4: Washed and Incubated: The embryo is washed and placed in an incubator to recover.
- Step 5: Checked for Viability: An embryologist evaluates how well the embryo survived thawing before proceeding with transfer.
What Are the Chances an Embryo Survives Thawing?
Most vitrified embryos survive the thawing process. With modern vitrification and warming techniques, survival rates commonly exceed 95%, although individual results can vary by embryo and fertility clinic.
Vitrification rapidly freezes embryos to minimize the formation of damaging ice crystals, resulting in much higher survival rates than older slow-freezing methods.
Surviving the thaw does not guarantee pregnancy. The embryo must remain viable, continue developing and successfully implant after transfer for pregnancy to occur.
What Happens If an Embryo Doesn’t Survive Thawing?
Can embryos be damaged during thawing? While rare with vitrification, an embryo occasionally doesn't survive the warming process.
If an embryo doesn't survive thawing, your fertility team will evaluate your backup options immediately. If you have additional frozen embryos, your doctor may recommend thawing a second embryo for transfer.
If no additional embryos remain, your doctor will discuss starting another IVF cycle or considering alternative options. Experiencing an unexpected loss is emotionally difficult, but having a clear backup plan provides direction during uncertain moments.
Embryo Quality After Thawing
Embryo thawing itself does not typically reduce embryo quality. Quality is largely determined before freezing by factors such as genetics, the age and quality of the egg, the embryo’s developmental stage and how it developed during IVF.
After thawing, embryologists evaluate viability, or how well the embryo survived the warming process. They examine factors such as cell survival, structure and whether the embryo begins re-expanding before proceeding with transfer.
For families who choose embryo genetic testing, options such as PGT-A are generally completed before freezing and can provide additional information about an embryo’s chromosomal status.
Pregnancy Success Rates for FET
Pregnancy success rates with frozen embryo transfer (FET) are generally comparable to, and in some cases higher than, fresh embryo transfers when a vitrified embryo survives warming. Success depends more on the embryo and transfer conditions than on the thawing process itself.
Several factors can influence frozen embryo transfer success rates, including:
The embryo’s development and chromosomal health. The health and preparation of the intended parent’s or gestational surrogate’s uterus. The age of the person providing the eggs when they were retrieved. The fertility clinic’s experience with vitrification, warming and embryo transfer.
How Long Between Thawing and Embryo Transfer?
Embryos are typically thawed about 2–4 hours before a frozen embryo transfer, giving the embryology team time to evaluate how well the embryo survived warming and prepare it for transfer.
The exact timing varies based on the embryo’s stage of development and your fertility clinic’s protocols. Your fertility clinic carefully coordinates the thaw with the transfer timeline to make sure the embryo is ready when it is time for the procedure.
When IVF Doesn’t Lead to Pregnancy, Surrogacy May Be the Next Step
For some intended parents, creating embryos through IVF is only part of the path to parenthood. After unsuccessful transfers, implantation challenges or medical concerns that make pregnancy unsafe, gestational surrogacy may provide another way to use embryos you have already created.
At American Surrogacy, we help families transition from fertility treatment into surrogacy with experienced support throughout the process. Our national recruitment efforts help us maintain an average 1–6 month match time, connecting intended parents with thoroughly screened surrogates sooner.
Our Limited Risk Program also provides unlimited rematching after qualifying disruptions without requiring you to pay our agency fees again. These protections can help preserve the time and resources you have already invested while keeping your path to parenthood moving forward.
Talk With American Surrogacy About Your Next Step
Unsuccessful transfers, recurrent pregnancy loss, implantation challenges or medical complications may change how you reach parenthood, but the embryos you have already created can still provide another path forward through gestational surrogacy.
Connect with an American Surrogacy specialist for a personalized consultation. We can help you understand how your frozen embryos may fit into a surrogacy journey and guide you through the next steps toward growing your family.