Fertility Treatments are usually performed using controlled ovarian hyperstimulation in order to obtain an adequate number of ovules and embryos.
The average number of embryos transferred is between 2 and 4, depending on the quality of embryos and woman's age.
If more embryos than the ones needed are obtained, these embryos are preserved using a technique known as cryopreservation, through which embryos are preserved at very low temperatures. This way, their metabolism is arrested and they can be preserved for a long time.
In this way, cryopreserved embryos can be thawed for later use. Transfer is usually usually takes place during the woman's normal ovulatory cycle.
The main advantages of cryopreservation are:
It reduces the risk of multiple pregnancy by storaging embryos that exceed an optimal number for transfer.
It allows to increase pregnancy rates. This is due to the fact that the embryos transferred are from previous cycles, as if the couple were performing more than one cycle of assisted conception.
It helps to reduce costs since ovarian hyperstimulation, oocyte retrieval, and fertilization are not needed for cryopreserved embryo transfer.
Spermatozoa as well as ovules can be cryopreserved. This treatment is offered to patients who present some kind of pathology or require treatments that could be a threat to the future fertility of the patient.