A frozen embryo transfer's chance of success tracks the age you were when that embryo was created and frozen — not your age on the day it's transferred. An embryo frozen at 32 and transferred at 38 carries odds much closer to a 32-year-old's than a 38-year-old's, because storage time itself doesn't age an embryo. Understanding this distinction is the key to reading any FET success-rate number honestly.
The number that actually predicts your outcome
Every embryo's genetic quality is set at the moment it's formed — from an egg retrieved on a specific day, at a specific age. Freezing pauses that embryo exactly as it is; it doesn't continue to age while it waits. So when you see a "frozen embryo transfer success rate by age" table, the age that matters is age at egg retrieval and freezing, not age at the transfer appointment.
This is why the same guidance in fresh vs frozen embryo transfer holds here too: storage duration is not a meaningful factor in outcomes. Embryos frozen for a few months and embryos frozen for several years, from the same age at freezing, perform in the same range.
Approximate live-birth rates per frozen transfer, by age at freezing
| Age at egg retrieval/freezing | Approximate live-birth rate per FET | What's driving the number |
|---|---|---|
| Under 35 | Roughly 45–55% | Egg and embryo quality are typically at their best at this age |
| 35–37 | A modest decline from the under-35 figure | Chromosomal abnormality rates begin a gradual rise |
| 38–40 | A further decline | A higher share of embryos from this age carry chromosomal issues |
| Over 40 | Considerably lower | The decline is sharpest here; embryos from a woman's own eggs at this age are less often chromosomally normal |
These are hedged, population-level ranges from published registry data (the same kind of sources behind IVF success rates by age) — not a personal prediction, and often somewhat higher than fresh-cycle per-transfer rates because FET selects for embryos that already survived to blastocyst and thaw successfully.
The birthday on your transfer calendar isn't the number that predicts your outcome — the birthday on your retrieval record is.
Why this distinction matters in practice
- Embryo banking. Freezing embryos from an earlier retrieval and using them later — after treatment for a medical condition, after building a family with an older sibling, or simply when ready — means those embryos carry the odds of the age they were frozen at, not the age at transfer.
- Comparing clinics' advertised numbers. A clinic reporting FET success "by age" may mean age at transfer or age at freezing; these give different pictures, especially for patients using embryos banked years earlier. Ask which one a quoted number reflects.
- Multiple frozen embryos from one retrieval. If you froze embryos at 33 and are transferring one at 36, your odds for that transfer track closer to your 33-year-old profile — the retrieval age, not the current one.
- Donor embryos or donor eggs. The same principle is why donor-egg cycles don't show the recipient's age-related decline — the relevant age is the donor's, at the time her eggs were retrieved.
What can still change the picture at transfer time
Age at freezing sets the embryo's genetic baseline, but a few things at the time of transfer still matter:
- The uterine lining's readiness — thickness and timing, prepared and checked before every FET regardless of how old the embryo is.
- The embryo's grade and stage — see embryo grading explained for what grading does and doesn't tell you; a top-graded embryo from an older retrieval and an average-graded one from a younger retrieval are different comparisons than age alone suggests.
- Whether the embryo was tested. If PGT confirmed a normal chromosome count, that embryo's odds are less about the age at freezing and more about the fact it already tested normal.
Frequently asked
If I freeze embryos now and transfer them in 5 years, do I get today's odds or the odds when I'm older?
Today's odds, for that specific batch of embryos — the embryo doesn't age in storage. Your uterus and overall health at the time of transfer still need to be ready, which your doctor will assess separately, but the embryo's own chromosomal quality reflects the age you were at retrieval.
Does this mean older patients should always bank embryos from a younger retrieval if they can?
It's one reason embryo banking or earlier fertility treatment can be a meaningful option to discuss, but it's a personal and medical decision — not a universal recommendation — since it depends on your specific situation, reserve, and family-building timeline. Talk it through with your doctor rather than acting on the general pattern alone.
Why do some FET success numbers look higher than fresh-cycle numbers at the same age?
Partly because FET rates are usually quoted per embryo transfer, using embryos that already proved they could reach blastocyst and survive a thaw — a more selected group than every egg retrieved in a fresh cycle. It isn't that freezing itself improves an embryo's chances.
Can I ask my clinic to tell me the age-at-freezing breakdown instead of age-at-transfer?
Yes — it's a reasonable, specific question, and a clinic that tracks its own data well should be able to answer it or explain which figure they report.