1. Egg retrieval
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 brief 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). Afterwards, one to three of the resulting embryos is transferred to the uterus.