Using frozen eggs to try for a pregnancy involves thawing the eggs in a lab, fertilizing them with sperm, growing the resulting embryos for several days, and then transferring one into your uterus. The entire process from the start of your preparation cycle to embryo transfer typically takes four to six weeks. It’s essentially an IVF cycle, but instead of retrieving fresh eggs, the lab works with eggs that have already been stored.
What Happens in the Lab During Thawing
Your frozen eggs are stored in liquid nitrogen at extremely low temperatures using a technique called vitrification, which flash-freezes them to prevent ice crystals from forming. When you’re ready to use them, an embryologist warms them through a carefully controlled series of solutions heated to body temperature (37°C). The entire warming process takes roughly 10 to 20 minutes, moving each egg through several solutions that gradually rehydrate it.
Not every egg survives thawing. Survival rates generally fall between 85% and 94%, depending on the specific warming protocol your clinic uses. So if you froze 12 eggs, you can reasonably expect 10 or 11 to survive. Your clinic will let you know how many made it through before moving to the next step.
Fertilization With ICSI
Frozen eggs require a specific fertilization method called ICSI, where an embryologist injects a single sperm directly into each egg. Standard IVF, where sperm and eggs are simply placed together in a dish, doesn’t work well with previously frozen eggs because the freezing process changes the outer shell of the egg, making it harder for sperm to penetrate on their own.
ICSI fertilization rates typically range from 50% to 80%. If 10 eggs survived thawing, you might end up with 5 to 8 fertilized eggs. From there, the embryos are cultured in the lab for five to six days until they reach a stage called blastocyst. Not all fertilized eggs make it to this point, so the number continues to narrow. This is a normal part of the process and doesn’t mean anything went wrong.
Optional Genetic Testing
Once embryos reach the blastocyst stage, you can choose to have them genetically screened before transfer. The most common type of testing checks whether each embryo has the correct number of chromosomes, which is one of the main reasons embryos fail to implant or result in early miscarriage. This testing is especially worth considering if you were 35 or older when your eggs were frozen, since the rate of chromosomal abnormalities in eggs rises with age.
During the biopsy, the embryologist removes a few cells from the outer layer of the embryo (the part that becomes the placenta, not the baby). The embryos are then re-frozen while the cells are sent to a genetics lab, with results usually back within one to two weeks. If you or your partner carry a known genetic condition, separate tests can screen for that specific disease.
Preparing Your Body for Transfer
While your embryos are being created in the lab (or after genetic testing results come back), your uterus needs to be ready to receive one. Most clinics use a hormone replacement protocol that gives you direct control over the timing. It works like this: you start taking estrogen early in your menstrual cycle, usually on day one through three. Some clinics prescribe a steady dose, while others gradually increase it over about two weeks. The estrogen thickens your uterine lining, and your doctor monitors it with ultrasound until it reaches at least 7 millimeters.
Once your lining is thick enough, you begin progesterone, which transforms the lining into a receptive state for an embryo. Progesterone is most commonly given as a vaginal insert or gel. The timing of your transfer is scheduled based on how many days of progesterone you’ve had, matching the developmental stage of your embryo.
An alternative approach uses mild ovarian stimulation with low-dose medications to trigger your body’s own hormone production rather than replacing hormones directly. Your doctor will recommend one approach based on your medical history, but pregnancy rates are comparable between the two methods.
The Transfer Itself
Embryo transfer is a quick outpatient procedure that usually takes about 10 to 15 minutes and doesn’t require anesthesia. A thin catheter is guided through your cervix using ultrasound, and the embryo is placed into your uterus. Most clinics transfer a single embryo to reduce the risk of twins. You’ll typically have a pregnancy blood test about 10 to 14 days later.
If you have extra viable embryos, they remain frozen for future use. This means one egg freezing cycle can potentially give you multiple transfer attempts.
The Full Timeline
If you’re using eggs you froze during a previous retrieval cycle, your clinic will likely ask you to wait at least one full menstrual cycle (about six to eight weeks) after retrieval before starting a transfer cycle. If your eggs have been in storage for months or years, you can begin whenever you’re ready.
A medicated transfer cycle runs roughly four to six weeks from start to finish. Some protocols begin with a short course of birth control pills the month before to synchronize your cycle. Then you’ll have about two weeks of estrogen, followed by several days of progesterone before the transfer day. If you’re adding genetic testing, build in an extra two to three weeks for biopsy results, since embryos are re-frozen during that window and transferred in a subsequent cycle.
Success Rates by Age at Freezing
The single biggest factor in your chances of success is how old you were when your eggs were frozen, not how old you are at transfer. Eggs frozen before age 35 offer the highest probability of a live birth, potentially up to 75% when enough eggs are available. Both the European Society of Human Reproduction and Embryology and the Nordic Fertility Society have identified freezing before 35 as the most cost-effective window.
For women who froze eggs before age 38, the live birth rate per transfer is roughly 38% to 48%. For those who froze at 38 or older, that rate drops to about 21% to 29% per transfer. One large cohort study found the live birth rate per transfer was over twice as high in the younger group. Regardless of age at freezing, having 15 or more eggs stored significantly improved the odds of at least one live birth.
Keep in mind that these are per-transfer rates. If you have multiple embryos, your cumulative chance across several transfers is higher than any single attempt.
What Frozen Eggs Cost to Use
The costs of using frozen eggs are separate from what you originally paid to retrieve and store them. At the University of Utah, for example, a frozen embryo transfer cycle runs about $3,500, covering ultrasound monitoring, the thaw, embryo preparation, and the transfer procedure. ICSI adds roughly $1,325. Genetic testing, medications, and any additional lab fees are typically extra. Total out-of-pocket costs for a single cycle often land between $5,000 and $8,000, though this varies widely by clinic and region. Some insurance plans now cover portions of fertility treatment, so it’s worth checking your specific policy.
Outcomes Compared to Fresh Eggs
Pregnancies from frozen eggs are largely comparable to those from fresh eggs, with one notable finding. A large analysis of U.S. fertility clinic data found that babies conceived from frozen eggs had a higher rate of high birth weight compared to fresh egg cycles: 12.5% versus 4.5% for women using their own eggs, and a similar pattern in donor egg cycles. The clinical significance of this difference is still being studied, but it’s not associated with major complications.
For women using their own frozen eggs, pregnancy and live birth rates were statistically similar to fresh cycles. In donor egg cycles, frozen eggs showed slightly lower live birth rates compared to fresh donor eggs. This distinction matters primarily if you’re choosing between a fresh and frozen donor egg program.