Before chemotherapy

Whether freezing oocytes before starting chemotherapy is sensible and even necessary depends largely on two main factors: the age of the patient at the start of therapy and the chemotherapeutic agent used. The dosage and duration of treatment also play a role here. In general, it can be said that, for example, the chances of young patients without cryopreservation of their eggs are often better than those of older patients, where the freezing of eggs is more often necessary to realize the desire for a child. In the case of chemotherapy with frequent administration cycles and high doses, egg freezing is usually recommended due to its strong effect on cell division. Ultimately, however, the decision as to whether cryopreservation is medically appropriate for the chosen form of therapy depends on the individual case and should be discussed with the team of doctors treating the patient.

How many oocytes should be frozen?

There is no general recommendation as to how many eggs should be frozen. However, it has been proven that a certain number of frozen eggs always fail to survive cryopreservation and perish. Therefore, the number of eggs frozen should not be considered to be the same as the number of attempts at potential pregnancy.

The probability of a successful pregnancy at a later stage increases with the number of cryopreserved eggs. Therefore, between 10 and 20 eggs are often frozen. The retrieval of such a high number of eggs can often only be achieved in several hormonal stimulation cycles with subsequent aspiration of the mature eggs

Is it possible to freeze already fertilized oocytes?

There are two types of cryopreservation of oocytes. The eggs can be frozen in both unfertilised and fertilised form. Common to both procedures is that the ovaries are first overstimulated with medication and hormones.

This causes the simultaneous, simultaneous maturation of several egg cells.These mature oocytes are then punctured from the ovary in a small procedure. Suitable eggs can then either be frozen directly or fertilized with the partner’s or donor’s semen using in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). In the so-called pronuclear stage, i.e. in the state of the not yet occurred fusion of maternal and paternal DNA, fertilized oocytes are frozen.

This is done after the addition of an antifreeze, which should prevent cell damage caused by ice crystals, using liquid nitrogen at a temperature of -196 degrees Celsius. If pregnancy is to begin, the fertilized eggs must first be thawed during a so-called thawing cycle (cryocycle). Not all cells are still able to develop after freezing. Those that are able to do so are transferred to the uterus in order to implant themselves there.