While freezing sperm cells and embryos (in the pronuclear, 8-cell or blastocyst stage) has long been established as a standard method, it was not clear until 2010 whether there is a similarly effective freezing method for unfertilised eggs.
Then, in 2010, the first European working groups were able to show that there are special freezing methods that can achieve similar pregnancy rates to fresh egg cells. Initially, freezing eggs (oocyte cryopreservation) was intended mainly for women dealing with the possibility of a loss of fertility as a side effect of upcoming treatment, such as chemotherapy. However, the technique is now used to offer women more flexible life planning as well. It means that women who cannot or who do not want to have children at the current time for private or professional reasons can have their eggs frozen and use them at a later time to get pregnant. The term ‘social freezing’ is now commonly used to designate egg freezing for non-medical reasons.
The number of eggs available to every woman is already fixed at birth. Since no new eggs are developed over the course of a woman’s life, this reserve of eggs shrinks over time.
This means that as a woman ages, two problems arise in terms of her fertility:
The older a woman is, the fewer eggs are available for successful ovulation. This reduces the chances of fertilisation.
Age also affects the quality of the eggs. As a rule of thumb, from around age 35, the likelihood of abnormalities, complications in pregnancy and miscarriages increases, and the chances of becoming pregnant are reduced. This development actually starts before a woman turns 35, although the risk of adverse effects is significantly lower in younger women.
Egg freezing can increase the chances of pregnancy at a later date by retrieving healthy eggs as early as possible and storing them.
Social freezing can be divided into three main stages:
If a woman decides to undergo social freezing, the first step is to retrieve as many eggs as possible. This usually involves hormone treatment to stimulate egg maturation. Regular ultrasound examinations allow the state of maturity of the egg follicles to be closely monitored. At the appropriate time, the eggs are then removed through the vagina under a short anaesthetic using a thin needle. The woman does not have to worry that her natural egg reserve will be reduced by this removal of several eggs. Each month a certain number of eggs become "receptive" to stimulation. Whereas in the natural cycle, a single follicle would prevail against the other follicles and the other eggs of this cycle would be lost, the stimulation accesses this otherwise lost monthly egg pool.
The retrieved eggs are frozen at minus 196 °C and can be safely stored in this state for decades. The more eggs that are stored, the greater the chance of being able to realise the desire to have a child later on. The most reliable studies currently available assume a 40% chance of a subsequent live birth with 10 stored eggs, a 60% chance with 12 eggs and a 90% chance with 20 eggs if they were retrieved in the optimal life phase (i.e. under 30 years of age).
If the wish to have a child is not fulfilled naturally, the couple can use cryopreserved eggs. These are fertilised with the partner's (or a sperm donor's) sperm outside the body (in vitro fertilisation). Subsequently, one to three of the resulting embryos are transferred into the uterus.
As the chances of natural pregnancy start decreasing from the age of 30, it is best to perform egg freezing as early as possible. The most reliable studies at the moment work on the basis of a 40% chance of a subsequent live birth for 10 stored eggs, 60% for 12 eggs and 90% for 20 eggs, if the eggs were retrieved at the optimal stage of life (i.e. when the woman was younger than 30).
Egg freezing does increase the likelihood of pregnancy at a later date, but cannot guarantee it. Thus, to further increase the chances, several eggs are usually frozen and stored. The older a woman is at the time of egg freezing, the lower the probability of a later pregnancy since the egg quality is already impaired. As many eggs as possible should be retrieved, which can be difficult in this situation since the egg reserve is often already reduced. Under certain circumstances, several hormone stimulations and egg retrievals may therefore be required.
Studies show that children conceived from frozen eggs are at a risk level comparable to that of children conceived during normal IVF/ICSI cycles. The hormone treatment required for egg freezing generally entails mild physical stress for women. These days, hyperstimulation rarely occurs thanks to the improved stimulation protocols. Individual consultation is part of the treatment.
The costs of egg freezing are not yet reimbursed by health insurance companies in Germany. However, an increasing number of employers are offering to cover some of the costs for their employees. In addition to the cost of hormone treatment and egg retrieval, fees are also charged for freezing the eggs and the yearly storage. When the frozen eggs are used, the cost of in vitro fertilisation is also added.