Egg Freezing

What is Egg Freezing?

Egg freezing, medically known as oocyte cryopreservation, is a fertility preservation technique that allows a woman’s eggs to be collected, frozen, and stored for future use. The eggs are not fertilised before freezing. When a woman decides to attempt pregnancy later, the eggs are thawed, fertilised with sperm in the laboratory through IVF, and the resulting embryo is transferred to the uterus.

Egg freezing provides an opportunity to preserve fertility at a younger age, when egg quality is typically higher. It does not guarantee pregnancy in the future, but it can improve the chance of having a biological child later in life.

What is Embryo Freezing?

Embryo freezing involves fertilising eggs with sperm before freezing. The fertilised eggs develop into embryos in the laboratory, and suitable embryos are then frozen for future transfer.

Embryo freezing has been used for decades and has very well-established success rates. It is commonly used during IVF treatment when more embryos are created than are needed for immediate transfer. These embryos can be stored and used in future cycles without needing another egg collection.

The key difference between egg and embryo freezing is that egg freezing preserves unfertilised eggs, while embryo freezing stores fertilised embryos.

Who is Suitable for Egg Freezing?

Egg freezing may be appropriate for:

• Women wishing to delay pregnancy: For personal, career, relationship, or medical reasons.
• Women diagnosed with cancer: Prior to chemotherapy or radiotherapy, which may damage ovarian function.
• Women with a family history of early menopause: To preserve fertility before ovarian reserve declines.
• Women with medical conditions affecting fertility: Such as severe endometriosis or autoimmune disorders.
• Women undergoing surgery involving the ovaries: Where ovarian tissue may be removed.
• Women with low ovarian reserve for their age: As identified on fertility testing.

Women in their early 30s or younger generally achieve better outcomes due to higher egg quality, although individual assessment is essential.

Who is Suitable for Embryo Freezing?

Embryo freezing may be considered for:

• Couples undergoing IVF: When additional embryos are available after a fresh transfer.
• Couples wishing to preserve embryos before cancer treatment.
• Individuals with a partner or donor sperm available: Who prefer the higher predictability of embryo survival and implantation rates.
• Those planning staged pregnancies: For example, spacing children over several years.

Embryo freezing requires a decision about sperm source and raises legal considerations regarding embryo ownership and use, which should be discussed carefully.

Benefits of Egg Freezing

• Fertility preservation: Allows women to store eggs at a younger biological age.
• Reproductive autonomy: Provides greater flexibility in family planning.
• Protection before medical treatment: Preserves fertility prior to chemotherapy or pelvic radiation.
• Reduced age-related risk: Eggs frozen earlier may reduce chromosomal abnormality risk compared to eggs produced at older ages.
• Future IVF opportunities: Enables multiple IVF attempts from a single egg collection cycle if enough eggs are retrieved.

Benefits of Embryo Freezing

• Higher survival rates after thawing: Embryos generally tolerate freezing and thawing well.
• Predictable outcomes: Embryo quality can be assessed before freezing.
• Avoids repeat stimulation cycles: Additional transfers can occur without another egg retrieval.
• Established success rates: Long-standing data support embryo freezing effectiveness.

Types of Freezing Techniques

• Slow Freezing: An older method involving gradual cooling. It has largely been replaced due to lower survival rates.
• Vitrification: A rapid freezing method that prevents ice crystal formation. It is now the standard technique for both eggs and embryos due to high survival rates after thawing.

What to Do Before Egg or Embryo Freezing?

Before proceeding, a comprehensive assessment is required.

• Initial consultation: Review of medical, surgical, and family history.
• Ovarian reserve testing: Blood tests such as AMH levels and antral follicle count via ultrasound.
• Infectious disease screening: Required before storage.
• Counselling: Discussion of expectations, emotional impact, legal considerations, and future plans.
• Partner or donor discussion (for embryo freezing): Including consent and legal documentation.
• Financial planning: Understanding procedure, medication, storage, and future IVF costs.

The Egg Freezing Process

• Ovarian stimulation: Daily hormone injections for 8–12 days to stimulate multiple eggs.
• Monitoring: Blood tests and ultrasounds every few days to track follicle growth.
• Trigger injection: Given when follicles reach the appropriate size to mature eggs.
• Egg retrieval: A short procedure under sedation using ultrasound guidance.
• Laboratory assessment: Mature eggs are identified and frozen using vitrification.
• Storage: Eggs are stored in liquid nitrogen tanks under regulated conditions.

The Embryo Freezing Process

The first steps mirror egg freezing, followed by:

• Fertilisation: Eggs are fertilised with sperm using IVF or ICSI.
• Embryo culture: Embryos grow in the lab for 3–5 days.
• Embryo grading: Embryologists assess quality.
• Freezing: Suitable embryos are vitrified and stored.

What to Expect After the Procedure?

After egg retrieval, mild symptoms are common:

• Bloating and abdominal discomfort: Usually settles within a few days.
• Light spotting: Mild vaginal bleeding may occur.
• Fatigue: Hormonal fluctuations can cause temporary tiredness.

Rare complications include ovarian hyperstimulation syndrome (OHSS), infection, or bleeding. Patients should contact their doctor if they experience severe pain, heavy bleeding, fever, or shortness of breath.

Egg and Embryo Freezing Success Rates

Success depends on age at freezing, number of eggs stored, and overall health.

For women under 35, approximately 20 frozen mature eggs may provide a reasonable chance of at least one live birth. Individual egg-to-birth rates vary.

Embryo freezing success rates are generally higher per embryo transferred compared to single thawed eggs, because embryo development has already occurred before freezing.

It is important to understand that freezing improves the opportunity but does not guarantee pregnancy.

How Long Can Eggs or Embryos Be Stored?

In Australia, storage is regulated by state legislation. Eggs and embryos may be stored for several years, with extension possible under certain conditions. Patients must maintain updated consent and contact information with the fertility clinic.

Risks and Considerations of Egg and Embryo Freezing

• No guarantee of pregnancy: Even with high-quality eggs or embryos.
• Age-related uterine factors: Freezing eggs does not prevent age-related pregnancy risks later in life.
• Emotional impact: Decisions may involve complex personal and ethical considerations.
• Legal implications: Particularly relevant for embryo storage if relationship circumstances change.
• Financial commitment: Ongoing storage and future treatment costs. Medicare rebate available if there is a medical indication.

Alternative Fertility Preservation Options

• Ovarian tissue freezing: Particularly for young cancer patients.
• GnRH agonist therapy: To temporarily suppress ovarian function during chemotherapy.
• Donor eggs or sperm: If ovarian reserve is low.
• Surrogacy: When carrying a pregnancy is not medically advisable.
• Adoption: An alternative pathway to parenthood.