Oocyte cryopreservation is the medical term for egg freezing, a procedure that preserves a woman’s unfertilized eggs for future use. The process involves stimulating the ovaries to produce multiple eggs, retrieving them, and then flash-freezing them at extremely low temperatures so they can be stored for years or even decades. The American Society for Reproductive Medicine (ASRM) removed the “experimental” label from the procedure in 2012 and now considers it an ethically permissible option for anyone looking to preserve their future fertility.
How Vitrification Works
The key breakthrough that made egg freezing practical is a technique called vitrification. Earlier methods used slow freezing, cooling eggs at a rate of about 0.3 to 2°C per minute. The problem with slow cooling is that water inside and around the egg can form ice crystals, which puncture cell membranes and destroy the egg. Balancing the rate of cooling to minimize crystal damage while avoiding other types of injury was extremely difficult, and survival rates were poor.
Vitrification takes a completely different approach. Instead of trying to manage ice formation, it eliminates ice entirely. The egg is placed in a high concentration of protective solution and then cooled at rates exceeding 20,000°C per minute. At that speed, water doesn’t have time to organize into crystals. Instead, it solidifies into a glass-like state, preserving the egg’s internal structure intact. The egg is then stored in liquid nitrogen at roughly -196°C, where biological activity effectively stops. When the time comes to use the egg, it’s warmed rapidly, reversing the process.
The Step-by-Step Process
Ovarian Stimulation
In a natural cycle, your body typically matures one egg per month. To make a freezing cycle worthwhile, fertility specialists use hormone medications to stimulate multiple eggs to develop at once. The most common approach is an antagonist protocol, where you inject a gonadotropin hormone daily for roughly 8 to 14 days. Around day six, or once follicles reach about 14 mm, a second medication is added to prevent your body from releasing the eggs too early. Throughout this phase, you’ll have several ultrasound appointments and blood draws so your doctor can track follicle growth and adjust your medication dose.
Some people use a minimal stimulation protocol with oral medications combined with lower doses of injectable hormones. This is a shorter course with fewer side effects but typically yields fewer eggs. For cancer patients who can’t afford weeks of delay, a “random-start” protocol can begin at any point in the menstrual cycle, allowing stimulation to start almost immediately after a cancer diagnosis.
Egg Retrieval
Once your follicles reach 16 to 18 mm, you receive a “trigger shot” that finalizes egg maturation. About 36 hours later, you go in for the retrieval itself. The procedure is done under intravenous sedation and takes roughly 20 to 30 minutes. Using ultrasound guidance, a thin needle is passed through the vaginal wall into each ovary, and the fluid inside each follicle is aspirated to collect the eggs. Not every follicle yields an egg; retrieval rates in the range of 70% to 85% of punctured follicles are typical. Most people go home the same day and return to normal activities within a day or two, though some cramping and bloating are common.
Freezing and Storage
Immediately after retrieval, embryologists assess the eggs for maturity. Mature eggs are placed in the cryoprotectant solution and vitrified within hours. The frozen eggs are stored in liquid nitrogen tanks, where they remain viable indefinitely in theory, though most clinics quote reliable storage timelines of 10 years or more. Annual storage fees typically run $500 to $1,000 per year.
Who Freezes Their Eggs
Egg freezing falls into two broad categories. Medical egg freezing is recommended before any treatment that could damage the ovaries. Chemotherapy, pelvic radiation, and certain surgeries can cause premature ovarian insufficiency, permanently reducing or eliminating fertility. Reproductive specialists recommend that all patients of reproductive age receive a fertility preservation consultation as early as possible before cancer treatment begins. Some genetic conditions and autoimmune diseases that affect ovarian function are also reasons to freeze eggs proactively.
Elective (sometimes called “social”) egg freezing is chosen by people who want children in the future but aren’t ready now. Common reasons include not having a partner, pursuing career or educational goals, or simply wanting more time. ASRM’s ethics committee has endorsed this use, concluding that planned egg freezing “may enhance reproductive autonomy and promote social equality” by giving people options they wouldn’t otherwise have.
Success Rates by Age
Age at the time of freezing is the single biggest factor in whether frozen eggs eventually lead to a baby. Eggs frozen at a younger age are more likely to be chromosomally normal, which directly affects fertilization, implantation, and live birth rates.
National data from the Society for Assisted Reproductive Technology (SART) gives a picture of what to expect when frozen eggs are later thawed and used. For women under 35 at the time of freezing, live birth rates per thaw cycle are approximately 46% to 48%. For women 35 to 37, rates are about 43% to 47%. For women 38 to 40, the range drops to roughly 40% to 45%. These numbers represent a single thaw cycle. Multiple cycles, and therefore more frozen eggs in storage, improve cumulative odds. Most fertility specialists suggest that freezing at least 10 to 15 mature eggs (for women under 35) provides a reasonable chance of at least one live birth.
It’s worth noting that these figures reflect outcomes after the eggs are thawed, fertilized, and transferred as embryos. Not every frozen egg survives thawing, not every surviving egg fertilizes successfully, and not every embryo implants. The funnel narrows at each step, which is why starting with more eggs matters.
Risks and Side Effects
The most talked-about risk of ovarian stimulation is ovarian hyperstimulation syndrome (OHSS), where the ovaries overrespond to hormones and swell painfully. Mild OHSS occurs in up to 5% of stimulation cycles and usually resolves on its own with rest and fluids. Moderate to severe OHSS affects about 1% to 5% of cycles and can cause significant abdominal bloating, nausea, and in rare cases, fluid buildup that requires medical attention. Severe OHSS occurs in roughly 0.5% of cycles. Fatal outcomes are extremely rare, estimated at about 1 in 50,000.
The retrieval procedure itself carries small risks of bleeding, infection, or injury to surrounding structures, but serious surgical complications are uncommon. During the stimulation phase, you may experience bloating, mood changes, headaches, and injection-site soreness. These side effects are temporary and resolve after the cycle ends.
Cost of Egg Freezing
A single egg freezing cycle in the United States typically costs $4,200 to $8,000 for the procedure itself. Stimulation medications add another $2,000 to $6,000, bringing the total for one cycle to roughly $6,000 to $14,000. Many people need more than one cycle to bank enough eggs, especially if they’re over 35 or have a lower ovarian reserve. Annual storage runs $500 to $1,000.
Insurance coverage varies widely. Some states mandate coverage for fertility preservation when it’s medically indicated (such as before cancer treatment), but elective freezing is rarely covered. A growing number of employers, particularly in the tech and finance sectors, now include egg freezing as a benefit, which has contributed to a sharp increase in the number of people pursuing it.