Egg freezing, also known as mature oocyte cryopreservation, is a method used to preserve reproductive potential in women.
Eggs are harvested from your ovaries, frozen unfertilized and stored for later use. A frozen egg can be thawed, combined with sperm in a lab and implanted in your uterus (in vitro fertilization).
Your doctor can help you understand how egg freezing works, the potential risks and whether this method of fertility preservation is right for you based on your personal and reproductive history.
Why it's done
Egg freezing might be an option if you're not ready to become pregnant now but want to try to ensure your ability to get pregnant or have a biological child in the future.
Unlike with fertilized egg freezing (embryo cryopreservation), egg freezing doesn't require sperm because the eggs won't be fertilized before they're frozen. Just as with embryo freezing, however, you'll need to use fertility drugs to induce ovulation so that you'll produce multiple eggs for retrieval.
You might consider egg freezing if:
- You're about to undergo treatment for cancer or another illness that may affect your future fertility potential. Certain medical treatments — such as radiation or chemotherapy — can harm your fertility. Egg freezing before treatment might allow you to have biological children at a later date.
- You're undergoing in vitro fertilization. If your partner isn't able to produce sufficient sperm on the day you have your eggs retrieved, egg freezing might be needed. When undergoing in vitro fertilization, some people prefer egg freezing to embryo freezing for religious or ethical reasons.
- You wish to preserve younger eggs now for future use. Freezing eggs at a younger age may help you preserve your ability to reproduce when the time is right in the future.
You can use your frozen eggs to try to conceive a biological child with sperm from a partner or a sperm donor. A donor can be known or anonymous. The embryo can also be implanted in the uterus of another person to carry the pregnancy (gestational carrier).
Egg freezing carries various risks, including:
- Conditions related to the use of fertility drugs. Rarely, use of injectable fertility drugs, such as synthetic follicle-stimulating hormone or luteinizing hormone to induce ovulation, can cause ovarian hyperstimulation syndrome — in which your ovaries become swollen and painful soon after ovulation or egg retrieval. Signs and symptoms include mild abdominal pain, bloating, nausea, vomiting and diarrhea. Even more rarely, it's possible to develop a more severe form of ovarian hyperstimulation syndrome that can also cause fluid to build up in your abdomen and shortness of breath.
- Egg retrieval procedure complications. Rarely, use of an aspirating needle to retrieve eggs causes bleeding, infection or damage to the bowel, bladder or a blood vessel. Risks associated with general anesthesia — which might be used for some egg retrieval procedures — also might pose a concern.
- Emotional risks. Egg freezing can provide false hope. Deciding to freeze your eggs may be empowering and provide hope for the future; however, there is still no guarantee of success.
If you use your frozen eggs to have a biological child, the risk of miscarriage will be primarily based on your age at the time your eggs were frozen.
Research to date hasn't shown an increase in the risk of birth defects for babies born as a result of egg freezing. However, further research is needed to confirm the safety of egg freezing.
How you prepare
If you're considering freezing your eggs, look for a fertility clinic with expertise in the field. These experts are commonly known as reproductive endocrinologists. The Centers for Disease Control and Prevention and the Society for Assisted Reproductive Technology provide information online about U.S. fertility clinics' individual pregnancy and live birth rates, although data related to pregnancies using frozen eggs is limited. Keep in mind, however, that a clinic's success rate depends on many factors, such as patients' ages.
If the expense of egg freezing is a concern, ask for detailed information about the costs associated with each step of the procedure and the annual storage fees.
Before beginning the egg-freezing process, you'll likely have some screening blood tests, including:
- Ovarian reserve testing. To determine the quantity and quality of your eggs, your doctor might test the concentration of follicle-stimulating hormone (FSH) and estradiol in your blood on day three of your menstrual cycle. Results can help predict how your ovaries will respond to fertility medication. Other blood tests and an ultrasound of the ovaries may be recommended to get a more complete assessment of ovarian function.
- Infectious disease screening. You'll be screened for certain infectious diseases, such as HIV. Potentially infectious eggs are stored differently than are other eggs.
Before going forward with egg freezing, consider important questions, including:
- When do you plan to become pregnant? Weigh the probability that you'll be able to become pregnant at that age against the probability of a successful pregnancy with the use of eggs that have been frozen.
- How many eggs would you like to freeze? Most fertility experts recommend freezing a total of 20 to 30 eggs and thawing six to eight eggs for each pregnancy attempt, depending on your age and egg quality. As a result your doctor may recommend that you undergo ovarian stimulation — in which you inject medication to stimulate your ovaries — more than once.
- What will you do with unused eggs? You might be able to donate unused frozen eggs to a couple or a research facility. You might also choose to discard unused eggs.
What you can expect
During the procedure
Egg freezing has multiple steps — ovulation induction, egg retrieval and freezing.
At the beginning of your menstrual cycle, you'll begin treatment with synthetic hormones to stimulate your ovaries to produce multiple eggs — rather than the single egg that normally develops each month. Several different medications might be needed, including:
- Medications for ovarian stimulation. To stimulate your ovaries, you might inject medication such as follicle-stimulating hormone (Follistim AQ, Gonal-f, Bravelle) or human menopausal gonadotropins (Menopur).
- Medications to prevent premature ovulation. To prevent premature ovulation, you might inject medication such as a gonadotropin-releasing hormone agonist (Lupron) or a gonadotropin-releasing hormone antagonist (Cetrotide).
During treatment, your doctor will have you return for follow-up visits. These visits will include having vaginal ultrasounds — a procedure that uses sound waves to create an image of the inside of your ovaries — to monitor the development of fluid-filled ovarian cysts where eggs mature (follicles). Blood tests also will be used to measure your response to ovarian-stimulation medications. Estrogen levels typically increase as follicles develop and progesterone levels remain low until after ovulation.
When the follicles are ready for egg retrieval — generally after eight to 14 days — injections of human chorionic gonadotropin (Pregnyl, Ovidrel) or other medications can help the eggs mature.
Egg retrieval is done under sedation, typically in your doctor's office or a clinic. A common approach is transvaginal ultrasound aspiration. During this procedure, an ultrasound probe is inserted into your vagina to identify the follicles. A needle is then guided through the vagina and into a follicle. A suction device connected to the needle is used to remove the egg from the follicle. Multiple eggs can be removed from your follicles in about 15 to 20 minutes.
After egg retrieval, you might experience cramping. Feelings of fullness or pressure might continue for weeks because your ovaries remain enlarged.
Shortly after your unfertilized eggs are harvested, they're cooled to subzero temperatures to stop all biological activity and preserve them for future use. The makeup of an unfertilized egg makes it more difficult to freeze and lead to a successful pregnancy than does the makeup of a fertilized egg (embryo). Your health care team might use substances called cryoprotectants to help prevent ice crystals from forming during the freezing process.
Cryoprotectants are mainly used with one of two freezing methods, including:
- Slow-freeze method. In this method, low concentrations of cryoprotectants are used initially. As the temperature is gradually reduced and the eggs' metabolic rates decline, higher concentrations of cryoprotectants are used. A slow-freeze method can also be used to protect eggs from potential exposure to toxins in the cryoprotectants.
- Vitrification. In this method, high initial concentrations of cryoprotectants are used in combination with cooling so rapid that intracellular ice crystals don't have time to form.
After the procedure
Typically, you can resume normal activities within a week of egg retrieval. Avoid unprotected sex to prevent unwanted pregnancy.
Contact your health care provider if you have:
- A fever higher than 101.5 F (38.6 C)
- Severe abdominal pain
- Weight gain of more than 2 pounds (0.9 kilograms) in 24 hours
- Heavy vaginal bleeding — filling more than two pads an hour
- Difficulty urinating
When you choose to use your frozen eggs, they'll be thawed, fertilized with sperm in a lab, and implanted in your or a gestational carrier's uterus.
Your health care team might recommend using a fertilization technique called intracytoplasmic sperm injection (ICSI). In ICSI, a single healthy sperm is injected directly into each mature egg.
About 90 percent of eggs survive freezing and thawing, and about 75 percent will be successfully fertilized. The chances of becoming pregnant after implantation are roughly 30 to 60 percent, depending on your age at the time of egg freezing. The older you are at the time of egg freezing, the lower the likelihood that you'll have a live birth in the future.
Keep in mind that pregnancy rates might be lower when frozen eggs are used, compared with fresh or frozen embryos.