Fresh vs Frozen Embryo Transfers: Know the Differences
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If you have been fortunate enough during an IVF cycle to have several eggs retrieved, fertilised with sperm, and good-quality embryos created, you may also have additional embryos to freeze for future use. This gives you the option to have with a fresh embryo transfer, and then if needed later, proceed with a frozen embryo transfer (FET).
Some ask why not make every embryo transfer cycle a fresh one. The reality is that when women undergo an IVF embryo transfer, the aim is to collect as many high-quality eggs as possible to increase the chance of pregnancy. IVF can be a physically and emotionally challenging process, so reducing the number of cycles is always beneficial.
Not every egg will fertilise or develop into a viable embryo, which is why being able to fertilise multiple eggs and potentially some embryos to freeze is fortunate and extends your pregnancy potential. Thanks to advances in IVF, success rates for fresh vs frozen embryo transfer are now considered comparable.
So, what is the difference between a fresh embryo transfer and a frozen embryo transfer? Let’s look at the facts.
What is a Fresh Embryo Transfer?
A fresh embryo transfer is an embryo transfer procedure that usually takes approximately 5 days after egg retrieval in an IVF cycle. The embryologist will discuss with you which embryo will be transferred and why. Because the embryos are transferred a few days after egg retrieval in the same cycle, there is no need to freeze and thaw the embryo, avoiding any thawing delays. The procedure is simple, usually performed at the clinic with or without ultrasound guidance, requires no anaesthetic, and most patients can resume normal activities the same day.
What is a Frozen Embryo Transfer (FET)?
Following a fresh embryo transfer, the embryologists aim to freeze as many remaining embryos as possible using a rapid freezing process called vitrification. Not all embryos are suitable for freezing, but those that are can be stored for future use in a frozen embryo transfer (FET). These embryos are stored in specialised storage tanks containing liquid nitrogen, which are continuously monitored by laboratory alarm systems to ensure they are kept at the correct temperature. Thawing is a simple process that takes around 15 minutes, where the blastocyst is removed from liquid nitrogen and carefully rehydrated.
Preparation for a FET cycle is generally easier than a fresh cycle, as it does not involve the same ovarian stimulation as used in a IVF cycle. Instead, the focus is on timing the transfer at the correct stage of your natural or medicated cycle. Your doctor will monitor the uterine lining at the beginning and again before transfer to ensure it is optimal for implantation.
On transfer day, the IVF embryo transfer procedure is the same as in a fresh cycle, requiring no sedation or anaesthetic, and you can usually resume normal activities straight away. Because of the way embryos are frozen, they can be thawed and transferred even several years after storage, while remaining as strong as the day they were frozen. Importantly, a frozen embryo transfer is also more cost-effective than a full IVF cycle, as only a portion of the treatment process is repeated.
Success Rates and Outcomes
Several factors affect the success of an embryo transfer, including Patient’s egg source age, embryo quality, and the health of the endometrial lining. At City Fertility, outcomes for both fresh and frozen transfers are comparable, thanks to laboratory methods and vitrification techniques. For more details, you can view our IVF success rates
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Frequently Asked Questions
Neither is inherently better. Both approaches can achieve successful pregnancies. The choice depends on factors such as your age, uterine readiness, and medical history. Your fertility specialist will recommend the best option for your unique situation.
A frozen embryo transfer may involve additional costs for freezing, storage, and thawing. There is also a small risk that some embryos may not survive the thawing process. However, vitrification has made survival rates very high.
Implantation time is not necessarily longer in fresh transfers. Instead, the success depends on synchronisation between the embryo’s development stage and the endometrial lining’s receptivity. When this alignment is optimal, implantation can occur in either fresh or frozen transfers.
Implantation time is not necessarily longer in fresh transfers. Instead, the success depends on synchronisation between the embryo’s development stage and the endometrial lining’s receptivity. When this alignment is optimal, implantation can occur in either fresh or frozen transfers.
