Egg freezing offers a real chance for women to preserve fertility, especially when done while young and with advanced technologies. If you do make the decision to freeze your eggs, let’s find out what the likelihood of a successful pregnancy is, dependent on a number of factors.
While factors like age at the time of freezing and number of eggs frozen significantly influence outcomes, one must also take into consideration age and fertility health at the time of retrieval, fertilisation and implantation.
When mainly looking at age at the time of freezing, younger women generally have better results. Freezing methods also matter. Advances in freezing technology, especially vitrification, outperform slow freezing, improving egg survival rates to 90-95%.
It has also been found that freezing 15 or more eggs can lead to a 68-82% chance of at least one live birth, depending on the age of the woman at the time of harvesting the eggs.
The success rate of egg freezing is primarily determined by two factors: your age at the time of freezing and the total number of eggs you are able to store.
Estimated Live Birth Rates by Age and Egg Count
Generally, the younger the eggs are, the higher their quality and the better the chance of a successful pregnancy later on.
| Age at Freezing | Number of Eggs Frozen | Estimated Chance of Live Birth |
|---|---|---|
| Under 35 | 10 eggs | ~60% |
| 15 - 20 eggs | 70% - 90% | |
| 35 – 37 | 15 eggs | ~70% |
| 20+ eggs | ~80% | |
| 38 – 40 | 10 eggs | ~30% |
| 20+ eggs | 70% - 75% | |
| Over 40 | 20 eggs | ~40% |
| 30+ eggs | ~50% |
The “Attrition” Process
Success rates are often discussed in terms of “attrition,” meaning that eggs are lost at each stage of the process when you return to use them.
- Thaw Survival: Modern “flash-freezing” (vitrification) has improved survival rates to approximately 90-95%.
- Fertilisation: Of the eggs that survive thawing, roughly 70-80% typically fertilise successfully.
- Embryo Development: About 40-60% of fertilised eggs successfully develop into a blastocyst (the stage ready for implantation).
- Live Birth: For women under 35, a single embryo transfer typically has a 30–45% chance of resulting in a live birth.
Key Considerations
- Quantity per Cycle: Younger women often retrieve more eggs per cycle (average 15-17) than women over 40 (average 7-9), which often means older women may need multiple cycles to reach a high probability of success.
- Return Rates: Interestingly, many women never return to use their frozen eggs; studies show return rates are only around 10-16%, often because they conceive naturally.
- Egg vs. Embryo Freezing: If you are in a long-term partnership, embryo freezing is sometimes associated with higher success rates because embryos are more stable during the freeze-thaw process.
Long awaited data has been obtained through a study described in this Extend Fertility article of an 8-year study (2016-2023) tracking 3,000+ women who froze eggs and 271 women who later used their own frozen eggs. It reconfirmed the two factors that have been though to significantly impact egg-freezing success, which are age at freezing (most important) and the number of eggs frozen
- Age is the biggest factor
Main takeaway: freezing earlier preserves “younger eggs,” even if used later.
Egg quality declines sharply with age:
Under 35: ~20–30% of eggs become healthy embryos; Up to ~89% success if enough eggs frozen
35-37: ~80% success
38-40: ~73% success
>40: Sharp drop; very few healthy embryos. By 43, almost none in this dataset.
- Success rates depend heavily on number of eggs
Main takeaway: each egg is another “chance,” so freezing more eggs significantly improves odds.
For women ≤40:
<10 eggs: ~58% success
10-14 eggs: ~67%
15-19 eggs: ~68%
20+ eggs: ~82%
- What happens to eggs after freezing
There’s attrition at every step, so starting with more eggs matters.
From 100 frozen eggs (approximate averages):
~91 survive thawing
~77 fertilised
~50% reach embryo stage
Age at freezing: under 35: ~25% become genetically normal embryos
- Technology has improved, but biology hasn’t
Egg survival rates now exceed 90% (better than older studies) and fertilisation and embryo development are also improved.
But:
Aging still reduces egg quality and technology can’t reverse age-related decline.
- Success rates by age (simplified guidance)
Before 35: Best outcomes, ~80%+ live birth rate if enough eggs frozen with 15-20 eggs often sufficient.
35-37: Still strong success (~75%) and good balance of timing compared to outcomes
38-40: ~54% success but need more eggs (often 20+)
After 40: Rapid decline in all measures with much lower probability of success
- How often women actually use frozen eggs?
Egg freezing is often a backup plan and not always used. Many conceive naturally and never use them.
Only ~10% returned to use them within ~4 years with an average return age of ~40
- Key biological insight
Eggs retain the age they were frozen at.
Example: Freeze at 34 → use at 40 = “34-year-old eggs”; Freeze at 40 → use at 40 = “40-year-old eggs”
This difference shows up in embryo quality, success rates and miscarriage risk.
Overall Take Away
Egg freezing offers a real chance for women to preserve fertility, especially when done young and with advanced technologies. It doesn’t guarantee the future but significantly boosts the chances of conception in later years. Best outcomes come from freezing earlier (ideally <35) and freezing enough eggs (often 15–20+).
Should you be considering preserving your fertility for your future, reach out to us here to book an appointment with our fertility specialists, to get the guidance you need.
