What the science says: a new study reveals the chances of becoming a mother using previously frozen eggs
More and more women are considering freezing their eggs. Not because they simply want to «delay» motherhood, but because many reach the age of 35—or are approaching 40—without having found the right time, the right partner, sufficient financial stability or the personal circumstances to have a child.
However, biology follows its own timeline. From the age of 35 onwards, both the number and quality of a woman’s eggs decline progressively, and at an increasingly faster rate. This is why egg vitrification—an ultra-rapid freezing technique—can be a valuable option for increasing the chances of having a biological child later in life.
But to what extent does this treatment actually «guarantee» success? How many women eventually use the eggs they have frozen? And what are the real chances of becoming a mother in the future using those eggs—particularly if that future is after the age of 40?
These are precisely the questions a team of researchers at Dexeus Mujer sought to answer. At the clinic, the demand for elective egg freezing—that is, for non-medical reasons—has increased rapidly in recent years, reflecting a clear social trend.
«Many women ask us for advice and guidance on this issue,» explains Dr Miquel Solé, biologist and Head of the Cryopreservation Laboratory at the Reproductive Medicine Department of Dexeus Mujer. «But until recently, we lacked enough information.» «Initially, egg vitrification was mainly offered to women with cancer and patients with medical conditions who wanted to preserve their fertility before treatment. We simply didn’t have enough women who had chosen to freeze their eggs electively, nor had enough time passed to assess how many would eventually return to use them. Once we had a sufficiently large group of patients and enough years of follow-up, we decided to carry out a retrospective study to answer these questions. The results have been very encouraging.»
More than half became mothers
The study, led by biologist and researcher Dr Miquel Solé, was presented this month at the 2026 Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE), one of the world’s leading scientific congresses in reproductive medicine.
The study provides several important findings:
- A total of 1,859 women who chose to freeze their eggs for non-medical reasons between 2012 and 2024 were followed.
- The average age at egg freezing was 36 years.
- Of these women, 30% had returned to use their frozen eggs by 2021.
- Women who froze their eggs between 2021 and 2024 were not included in this analysis because insufficient time had passed to evaluate whether they would eventually return for treatment.
- The average age at thawing was 41 years.
- Overall, 12% did not obtain viable embryos, whereas 88% successfully developed viable embryos.
- Among those women, and based on the treatments completed so far (as not all frozen embryos have yet been transferred), 70% achieved pregnancy, and more than 50% have already given birth, fulfilling their wish to become mothers.
What do these results show?
These findings are particularly significant because the so-called «return rate»—the proportion of women who eventually come back to use their frozen eggs—has traditionally been low. In fact, only a limited number of scientific studies have examined this issue using large patient cohorts.
A systematic review published in the journal Human Reproduction Update, entitled Planned oocyte cryopreservation: a systematic review and meta-regression analysis, analysed data from 8,750 women and estimated an average return rate of 11.1%. Among those who eventually used their frozen eggs, the live birth rate was 28%. However, this figure increased to approximately 52% when the eggs had been frozen before the age of 35, confirming that the woman’s age at the time of vitrification is the single most important factor in predicting success.
Both the findings of this review and the study conducted by Dexeus Mujer suggest that egg freezing is an effective strategy for women who expect to postpone motherhood—provided that the eggs are vitrified at a relatively young age. Freezing eggs before the age of 35 increases by approximately tenfold the chances of having a biological child compared with attempting natural conception at the age of 40, when the likelihood of pregnancy is generally below 5%. It also doubles the chances of having a baby at that age using assisted reproductive treatments with one’s own eggs—which have naturally aged over time. According to the latest report published by the Spanish Fertility Society (SEF), only 13.5% of women aged 40 or over achieve a live birth using their own fresh eggs. Age, therefore, matters. «Freezing eggs at the age of 39 or 40 does not offer the same chances of success as doing so before the age of 35. Egg freezing does not stop a woman’s reproductive ageing, but it does preserve her eggs at the age they were when they were vitrified,» explains Dr Marta Devesa, Head of the Reproductive Medicine Department at Dexeus Mujer.
So, is egg freezing worth it?
The answer depends on each woman’s individual circumstances. However, scientific evidence consistently points to one important conclusion: egg freezing does not guarantee a future pregnancy, but it can significantly increase the chances of having a biological child using one’s own eggs—particularly when the procedure is carried out before the age of 35.
For this reason, fertility specialists increasingly prefer to talk about planning motherhood with accurate information, rather than simply postponing it.
So, if having children is something you hope for—even if not in the immediate future—it is advisable to seek information before the age of 35. Ask your gynaecologist to assess your ovarian reserve. If your ovarian reserve is low, or if you believe you may need to delay motherhood, consult a fertility specialist to discuss your options.
Having reliable, personalised information is essential. It allows you to understand the different possibilities available, reduce uncertainty and make the decision that best suits your circumstances. Because preserving fertility is not about stopping time—it is about creating more opportunities for the future.
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Frequently Asked Questions
What is the best age to freeze eggs?
Current evidence indicates that the best balance between clinical effectiveness and future benefit is achieved when eggs are frozen before the age of 35.
Does egg freezing guarantee pregnancy?
No. Egg freezing does not guarantee pregnancy or the birth of a child.
Vitrification preserves the reproductive potential of the eggs, but the chances of success depend on several factors, including:
- the woman’s age at the time the eggs were frozen;
- the number of eggs stored;
- egg survival after warming;
- successful fertilisation and embryo development;
- embryo quality;
- uterine receptivity and other reproductive factors.
Scientific societies emphasise that women should receive clear and realistic counselling. Egg freezing can improve future reproductive opportunities, but it should not be regarded as an «insurance policy» for fertility.
How long can eggs remain frozen?
Thanks to current vitrification technology, eggs can remain frozen for many years without the length of storage appearing to affect their viability.
Stored in liquid nitrogen at ?196°C, all biological activity is effectively halted, meaning that cellular ageing is suspended. The available scientific evidence also indicates that the length of time eggs remain frozen is not associated with lower survival or pregnancy rates, although most of the published data relate to storage periods of up to 20 years.
What is the survival rate of frozen eggs after thawing?
Thanks to vitrification, egg survival after warming is now very high.
Data from specialised fertility centres and systematic reviews consistently report survival rates of between 85% and 95%, with rates exceeding 90% in laboratories with extensive experience.
However, these figures may vary depending on several factors, including:
- the woman’s age when the eggs were frozen;
- the initial quality of the eggs;
- the laboratory’s experience;
- the vitrification and warming protocols used.
How many eggs should be frozen to maximise the chances of success?
The number of eggs frozen and the woman’s age at the time of vitrification are the two factors that have the greatest influence on the likelihood of having a child in the future.
In general, the more eggs that are frozen—and the younger the woman is at the time of the procedure—the higher the chances of success.
As a general guide:
- Women under 35 years of age: freezing 15–20 mature eggs (MII) offers a high probability of achieving at least one live birth (in many predictive models, more than 70–80%).
- Women aged 35–37 years: it is generally recommended to freeze 20 or more eggs, as egg quality begins to decline.
- Women aged 38 years and over: 25–30 eggs or more may be required to achieve similar chances of success, which often means undergoing more than one ovarian stimulation cycle.
When is fertility preservation recommended?
Egg freezing is particularly recommended when there is a significant risk of losing ovarian function or when motherhood is expected to be postponed.
The main recognised indications include:
- before undergoing cancer treatment;
- before certain types of ovarian surgery, including some cases of endometriosis;
- for women at risk of premature ovarian insufficiency due to genetic or medical conditions;
- when motherhood is likely to be delayed for personal or professional reasons, particularly in women under the age of 35 who wish to maximise their future reproductive options.
