There’s an ongoing discussion in fertility medicine: which is “better” fresh embryo transfers or frozen embryo transfers (FETs)? Many fertility clinics and specialists believe FETs provide higher pregnancy success rates. However, and this is critical, success rates are not the only factor to think through; choosing between fresh and frozen depends heavily on your individual circumstances.
In FET for in vitro fertilisation (IVF), pregnancy success rate depends on a number of factors, most particularly the woman’s age. See this article by IVF Australia, specific to their population, interestingly demonstrating the correlation between fresh and frozen embryo transfer and age.
Another key element is how the embryos are frozen, as defined by this article from Life Fertility Clinic: some embryos (or possibly all embryos) will not survive the freezing and thawing process if cells are damaged. Frozen embryo survival rates are more than 90% if embryos are frozen by vitrification at the blastocyst stage (5–6 days after fertilisation). If they are frozen at the earlier stages by slow freezing, approximately 80% survive the freezing and thawing process.
If an embryo vitrified at the blastocyst stage is thawed and transferred, it has approximately the same success rate as a fresh embryo. There is no evidence that frozen and thawed embryos result in a greater number of miscarriages or abnormalities.
Other fertility-related conditions can also influence the success of FET, as defined in this article by the Pacific Fertility Center LA (PFCLA), which also lists five benefits of FET.
How the two procedures differ
In a fresh transfer, after stimulation, egg retrieval and fertilisation, an embryo can be transferred back into the uterus 3–5 days later. In contrast, a frozen embryo transfer (FET) involves freezing (cryopreserving) the embryos first and then thawing and transferring them later potentially much later, when the timing is right.
Evidence on success rates
Studies have shown that some patient groups benefit more from FET than fresh transfers. For example, a study in the New England Journal of Medicine found that women with PCOS had higher live-birth rates when using frozen embryos. But there is also contradictory evidence: a British Medical Journal study found no significant difference in ongoing pregnancy or live-birth rates for women without certain hormonal issues. Another study suggests that in older women, if the embryo quality is very good, fresh transfers work just as well.
Other important factors beyond success rates
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Age: both yours and the partner’s age, or that of a donor, because age affects embryo quality.
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Sperm quality: this affects fertilisation and overall embryo health.
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Health during transfer: your physical condition matters for both types of cycles.
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Quality of embryos: the quality of an embryo (how healthy or viable it is) has a big impact on live-birth chances, whether fresh or frozen. PFCLA cites data showing very high live-birth rates (~79%) for good-quality embryos, while poor-quality embryos might only yield ~28%.
Benefits of frozen embryo transfers (FET)
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Cost-effectiveness: if you have more embryos to use later, you don’t need another egg retrieval, which saves money and stress.
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Flexibility in timing: you can choose when to do the transfer, which is helpful for personal or medical reasons (e.g., delaying a pregnancy).
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Less physical/mental stress: no repeated stimulation cycles; only the uterine-lining preparation medicines are needed for the transfer.
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More natural uterine environment: because FET doesn’t happen immediately after ovarian stimulation, hormone levels (like oestrogen) may be more optimal, which could improve the uterus’s receptivity.
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Genetic testing: with frozen embryos, there’s more opportunity to do PGD/PGS/PGT-A (embryo genetic screening) before transfer, which potentially improves success and reduces miscarriage risk.
Recommendation
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It is strongly advised to talk to your fertility clinic or specialist, because the best path depends on your situation.
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It is advisable to ask about the success rates of the clinic that you are opting for.
Key take-aways
- FET is increasingly popular and often more successful or advantageous in many cases, but it’s not a one-size-fits-all solution.
- The “higher success” narrative for FET is true in some cases, but not for everyone.
- Individual factors like age, embryo quality, health, and what you’re comfortable with (cost, timing) are just as important, if not more, than raw success rate statistics.
- Good communication with your fertility clinic is crucial. Ask about their data, their approach, and how it relates to your specific fertility profile.
