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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. With age, this reserve of eggs shrinks.
This means that as a woman ages, two problems arise in terms of her fertility:
1. The older a woman is, the fewer eggs are available for successful ovulation. This reduces the chances of fertilisation.
2. 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.
Egg freezing can be broken down into three major stages:
If a woman opts for egg freezing, the first step is to retrieve as many eggs as possible. To do this, hormone treatment is usually performed to stimulate egg maturation. Regular ultrasound scans allow for accurate observation of the state of maturity of the egg follicles. At an appropriate time, the eggs are then removed vaginally using a thin needle under local anaesthesia. The woman does not need to worry about her natural reserve of eggs being reduced by this removal of multiple eggs. Each month, a certain number of eggs becomes ‘receptive’ to stimulation. Whilst in the natural cycle a single follicle would prevail against the other follicles and the other eggs in this cycle would be lost, stimulation accesses this monthly pool of eggs that would otherwise be lost.
The retrieved eggs are frozen at -196 °C and can be safely stored for decades in this state. The more eggs are stored, the greater the chance of having children at a later date. 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).
If the couple are unable to have children by natural means later, they can fall back on the cryopreserved eggs. These are fertilised outside the body (in vitro fertilisation) using the partner’s sperm (or sperm from a sperm donor) and and afterwards the 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 any more thanks to the improved stimulation protocols. Individual consultation is part of the treatment.