Fertility Preservation with the Advanced Egg Freezing Technology

Dr. TANG Oi Shan

Honorary Consultant in Obstetrics & Gynaecology

Specialist in Reproductive Medicine

As the name implies, “egg freezing” is to freeze the eggs of a woman, so as to preserve the fertility at the current status. Later on, the woman may use the frozen eggs to get pregnant via fertility treatment if necessary. In the past, egg freezing technology was mostly used by women who either temporarily or permanently lose their fertility due to diseases or other medical treatments, e.g. cancer patients requiring chemotherapy. They may then freeze their eggs prior to their treatment and subsequently use their frozen eggs for reproduction at a later stage after recovery from illnesses.

Recently, egg freezing has become more socially acceptable. With the advance in the techniques of ovarian stimulation and egg collection, egg freezing has become a safe and well-established method of fertility preservation. More and more healthy young women would consider using this method to preserve their fertility.

Improvement in Survival Rate of Frozen Eggs with Ultra-rapid Vitrification

In the past, egg freezing was carried out by “slow freezing” method, which may damage the structure of the eggs, and thus affecting the survival, fertilisation potential and live birth rate from the frozen eggs.

The new ultra-rapid freezing technique (also known as vitrification) causes very minimal damage to the eggs and the survival rate of frozen eggs is higher than 90%. The live birth rate from the frozen eggs is also comparable to that of fresh eggs when they are used for in-vitro fertilization (IVF) treatment. Thus egg freezing has been used as a regular service for fertility preservation.

The “Optimal Age” to Consider Egg Freezing: Around 35 Years Old

The live birth rate from frozen eggs is closely related to the egg quality which tends to be better if the eggs are collected and frozen at a younger age. The “optimal age” for egg freezing is a balance between the possibility of achieving natural conception at a younger age and the deterioration of egg quality as the woman gets older. Besides, in Hong Kong, the law only allows the storage of one’s eggs for a maximum of 10 years. Taking all these into consideration, the “optimal age” to consider egg freezing for an average woman is around 35 years old. However, for any particular individual woman, who, because of diseases or family history, worries that her egg reserve is poorer than average, a blood test for ovarian reserve (AMH) may be performed. Egg freezing may then be performed at an earlier age if indicated.

Egg Freezing Procedure

In order to obtain eggs for freezing, the woman has to receive injections to stimulate the ovaries for around 8 to 10 days to produce more eggs and then an egg collection procedure would be performed to take the eggs out of the body by passing a needle through the vagina. The procedure may cause some discomfort and risks (e.g. ovarian hyperstimulation syndrome). Thanks to the recent advance in surgical technique and pharmacology (e.g. ovarian trigger using GnRH agonist), the risks of egg freezing can be kept to a minimal. Nowadays, egg freezing has become an acceptable procedure for most women who want to preserve their fertility and they can choose to undergo the required number of cycles of treatment to obtain the number of eggs they want to keep for future use.

The advance in egg freezing technology provides an opportunity for women who want to preserve their eggs for future use. However, it may not guarantee the egg quality and live birth rate after thawing of the eggs. The woman may still require fertility or IVF treatment later at a more advanced age.

It is important for women who intend to use egg freezing to preserve their fertility to know that the chance of pregnancy by using frozen eggs would not be better than natural conception at the moment of egg freezing. Overall speaking, it is still advisable for women to get pregnant at an early age if feasible.

Does Egg Freezing Disturb Menstrual Cycles, Cause Aging or Speed Up Menopause?

A woman produces a set number of eggs each cycle and egg freezing procedure only harvests the cohort of eggs of the current cycle. It does not affect the “future eggs”, therefore it would not affect the future menstrual cycles, and it would not cause aging or early menopause.