The egg cell is the largest cell in the human body. It contains a large volume of cytoplasm and fluid, making it difficult to freeze using standard slow-freezing methods without the risk of ice microcrystals forming. To avoid damage to cellular structures, vitrification—that is, instantaneous, ultra-rapid freezing—is used for long-term storage.
The chances of successfully giving birth to a healthy child when using vitrified oocytes are determined by two key factors:
- The woman’s age at the time of retrieval and cryopreservation of the cells.
- The total number of mature oocytes obtained and preserved.
The required number of MII-stage oocytes at different ages
To achieve reliable results, the following clinical guidelines apply depending on age:
- A woman aged 35 typically needs to undergo 1–2 cycles of ovarian stimulation to preserve at least 16 mature oocytes in the second stage of meiosis (MII). This provides an 80–85% probability of giving birth to one healthy child in the future.
- Women under 38 years of age need to cryopreserve 18 to 20 MII oocytes to have a 70–80% chance of giving birth to one healthy baby.
- Women aged 38–40 need to freeze 25 to 30 MII oocytes for a 65–75% probability of giving birth to one child.
There is a precise predictive model for the probability of having children based on age. It clearly illustrates the difference: if three women aged 34, 37, and 42 cryopreserve the same number of cells (20 mature oocytes each), the probability of giving birth to one child will be 90%, 75%, and 37%, respectively.
Probability of Having a Child Based on Age and Number of Eggs
Precise estimates of successful births depend directly on the patient’s reproductive age at the time of egg retrieval and the total volume of frozen biological material. The statistics on the chances of having a child are distributed as follows:
- For a 30-year-old: freezing 5 oocytes yields a 64% probability; 10 oocytes increase the chance to 87%; 15 oocytes provide a 95% probability; 20 oocytes yield a 98% probability; and with 25 oocytes, the probability reaches 99%.
- At age 32: freezing 5 oocytes results in a 55% chance; freezing 10 oocytes increases the chance to 80%; having 15 oocytes yields a 91% chance; 20 oocytes guarantee a 96% chance; and 25 oocytes ensure a 98% success rate.
- For women aged 34: freezing 5 oocytes yields a 47% success rate; 10 oocytes yield 72%; 15 oocytes yield 85%; 20 oocytes yield 92%; and a reserve of 25 oocytes yields a 96% success rate.
- For a 36-year-old: with 5 oocytes, the probability is 40%; freezing 10 oocytes yields a 64% success rate; 15 oocytes yield 78%; 20 oocytes increase the success rate to 87%; and 25 oocytes yield 92%.
- For a 38-year-old: freezing 5 oocytes results in a 26% success rate; 10 oocytes yield 44%; 15 oocytes yield 59%; a reserve of 20 oocytes guarantees 69%; and 25 oocytes yield a 77% probability.
- For women aged 40: having 5 oocytes yields only a 17% chance, 10 oocytes yield 31%, 15 oocytes raise the rate to 42%, 20 oocytes yield 52%, and 25 oocytes yield a 60% chance.
- For a 42-year-old: having 5 oocytes yields only a 10% chance, 10 oocytes yield 19%, 15 oocytes guarantee 28%, 20 oocytes yield a 35% probability, and 25 oocytes yield a 42% probability.
These figures confirm that at a young age, even a relatively small supply of oocytes yields high success rates. For example, for a 30-year-old woman, having 10 oocytes already ensures an 87% success rate, whereas at age 40, even 20 preserved oocytes yield only a 52% probability.
Advantages of Cryopreservation Before Age 35
Reproductive outcomes are significantly higher for women aged 35 and younger at the time of oocyte cryopreservation compared to patients in the older age group.
Women over the age of 35 often require more than one cycle of ovarian stimulation to collect a sufficient number of eggs and achieve a high probability of a successful birth. Clinical data show that the overall success rate—including ongoing pregnancies and live births—drops significantly if a woman is over 40 years old at the time of vitrification.
From both a financial and medical standpoint, the FERTIFREEZE Fertility Preservation program is most beneficial and effective for women under the age of 35. During this period, ovarian reserve is at a healthy level, so a single standard stimulation cycle can yield the necessary number of high-quality oocytes for freezing with maximum reproductive potential.
The likelihood that frozen oocytes will be needed increases as a woman ages, and after age 35, it exceeds 61%. Most patients surveyed confirm that they do not regret participating in the deferred motherhood program, viewing the preserved oocytes as reliable insurance against the risk of infertility.
The Effect of Storage Duration on the Health of the Future Child
The length of time oocytes are stored in a cryobank does not negatively affect the risk of aneuploidy—that is, abnormalities in the chromosome set of the future embryo. Long-term storage does not alter gene expression profiles in thawed cells. Furthermore, studies have not identified an increase in obstetric or perinatal complications in pregnancies achieved using vitrified oocytes compared to standard programs.
ART Programs for Declining Fertility
When a woman’s own oocyte reserve is depleted or their quality—due to age or medical conditions—prevents the formation of a viable embryo, modern reproductive medicine offers several effective protocols.
The primary approach is IVF (in vitro fertilization), which involves the fertilization of a woman’s own eggs with her spouse’s or partner’s sperm in a laboratory setting. The resulting embryos are cultured in incubators until the blastocyst stage, after which one embryo is transferred to the uterine cavity, and the remaining ones are vitrified. This method is effective as long as the ovaries are capable of producing a sufficient number of mature and genetically sound cells. However, after age 40–42, the success rate of the standard protocol using the woman’s own oocytes drops sharply due to a high rate of chromosomal abnormalities.
If the woman’s own oocyte reserve is depleted, she has entered early menopause, or repeated standard attempts have been unsuccessful, patients are recommended to undergo IVF with egg donation. Eggs from young, physically and mentally healthy female donors under the age of 32 who have undergone comprehensive genetic and infectious disease screening are used for fertilization. The retrieved oocytes are fertilized with the partner’s sperm. Thanks to the high quality of the donor biomaterial, the probability of achieving a clinical pregnancy and a successful delivery in such protocols exceeds 60–65% on the very first attempt, regardless of the prospective mother’s age.
In cases where severe combined forms of infertility have been diagnosed or both partners lack gametes, IVF with dual donation becomes the solution. This option is also relevant for single women with significantly depleted ovarian reserve or a high risk of transmitting severe hereditary disorders. As part of the program, embryologists fertilize a donor egg with sperm from a screened donor, after which the resulting high-grade embryo is transferred to the patient’s uterus for subsequent gestation and natural delivery.
Frequently Asked Questions
At what age is it best to freeze eggs?
The most favorable period is before age 35, primarily between 28 and 34 years old. During this time, the ovarian reserve is sufficiently large, chromosomal abnormalities in oocytes occur less frequently, and a single egg retrieval is usually sufficient to obtain an adequate supply of eggs.
How long can eggs remain frozen?
The biological material is stored in liquid nitrogen at a constant temperature of minus 196 degrees. Under these conditions, all metabolic processes cease completely, allowing the cells to retain their original quality for years and even decades with no time limit.
Does the procedure offer an absolute guarantee of having a child?
In reproductive medicine, it is impossible to offer a 100% guarantee, since embryo implantation and pregnancy are influenced by the prospective mother’s overall health. Nevertheless, cryopreservation of 15–20 oocytes before the age of 35 offers a success rate of up to 95–98%, which is the highest achievable rate in medicine.
Does egg retrieval deplete a woman’s ovarian reserve?
No, the retrieval procedure does not deplete the natural egg supply any faster than normal. In every natural cycle, the body activates a group of follicles, but only one ovulates, while the rest regress and die. Stimulation merely helps those cells mature that the body would have lost that month anyway.
What happens to the biological material if pregnancy occurs naturally?
If a woman successfully becomes pregnant and gives birth naturally, the preserved oocytes remain in cryopreservation. They can be used later to have a second or third child, donated to a donor program if desired, or disposed of upon written request.
