How many eggs should be frozen to have a high probability of having a healthy baby?

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 the standard slow-freezing method without risking the formation of ice microcrystals. To avoid damage to cellular structures, vitrification—a process of instantaneous, ultra-rapid freezing—is used for long-term storage.

The chances of successfully having a healthy baby using vitrified oocytes are determined by two key factors:

1. The woman's age when the cells are retrieved and cryopreserved.
2. The total number of mature eggs retrieved and stored.

Number of MII-stage oocytes needed at different ages

The following clinical guidelines apply to achieve a reliable outcome, depending on age:

• A 35-year-old woman typically needs to undergo 1–2 ovarian stimulation cycles to store at least 16 mature oocytes at the second stage of meiosis (MII). This provides an 80–85% chance of having one healthy child in the future.
• Women under 38 need to cryopreserve 18 to 20 MII oocytes to have a 70–80% chance of having one healthy baby.
• Women aged 38–40 need to freeze 25 to 30 MII oocytes for a 65–75% chance of having one child.

There is a precise predictive model for the likelihood of having children based on age. It clearly shows the difference: if three women aged 34, 37, and 42 cryopreserve the same number of cells (20 mature oocytes each), their chances of having one child will be 90%, 75%, and 37%, respectively.

Chance of having a child based on age and number of eggs

The table shows precise calculated probabilities, in percent, of having a child based on reproductive age at the time of egg retrieval and the total number of cryopreserved eggs:

These figures confirm that at a younger age, even a relatively small number of eggs can yield a high success rate. For example, 10 oocytes give a 30-year-old woman an 87% chance of success, while at age 40, even 20 stored cells give only a 52% chance.

Benefits of cryopreservation before age 35

Reproductive outcomes are significantly better for women who are 35 or younger when their oocytes are cryopreserved than for patients in older age groups.

After age 35, more than one ovarian stimulation cycle is often needed to accumulate enough eggs and achieve a high chance of a successful birth. Clinical data show that the overall rate of positive outcomes, including ongoing pregnancies and live births, declines significantly if a woman is over 40 when her eggs are vitrified.

From both a financial and medical perspective, the FERTIFREEZE Fertility Preservation program is most cost-effective and successful before age 35. During this period, ovarian reserve is at a good level, so a single standard stimulation cycle can yield the required number of high-quality eggs for freezing, with maximum reproductive potential.

The likelihood of frozen eggs being needed increases as a woman gets older, exceeding 61% after age 35. Most patients surveyed say they do not regret participating in the delayed motherhood program, viewing their stored cells as reliable insurance against the risk of infertility.

How storage duration affects the health of a future child

The length of time oocytes are stored in a cryobank does not negatively affect the risk of aneuploidy—that is, an abnormal number of chromosomes in a future embryo. Long-term storage does not alter gene expression profiles in thawed cells. Studies have also found no increase in obstetric or perinatal complications in pregnancies achieved using vitrified oocytes compared with standard programs.

Frequently asked questions

What is the best age to freeze eggs?

The most favorable period is before age 35, particularly between 28 and 34. During this age range, ovarian reserve is sufficiently high, chromosomal abnormalities in oocytes are less common, and one egg retrieval is usually enough to build an adequate supply.

How long can eggs remain frozen?

Biological material is stored in liquid nitrogen at a constant temperature of minus 196 degrees. Under these conditions, all metabolic processes stop completely, allowing the cells to retain their original quality for years or even decades, with no time limit.

Does the procedure guarantee that I will have a child?

In reproductive medicine, a 100% guarantee is impossible because the mother's overall health affects embryo implantation and carrying a pregnancy to term. Nevertheless, cryopreserving 15–20 oocytes before age 35 gives a success rate of up to 95–98%, the highest achievable figure in medicine.

Does egg retrieval deplete a woman's ovarian reserve?

No. Egg retrieval does not deplete the natural supply of eggs faster than time alone would. In each natural cycle, the body activates a group of follicles, but only one ovulates; the others are reabsorbed and die. Stimulation simply helps the eggs mature that the body would have lost anyway that month.

What happens to the biological material if I become pregnant naturally?

If a woman becomes pregnant successfully and gives birth naturally, her stored oocytes remain in the cryobank. They can be used later to have a second or third child, donated to a donor program if she wishes, or discarded upon written request.