CRYOPRESERVATION OF EMBRYOS
It is a method by which we freeze the excess but good quality embryos, that is, embryos that are not transferred to the uterus. In this way, the couple is provided with a second chance, a second embryo transfer, in case the first one fails or still has the opportunity to have a second child without the need of repeating ovarian stimulation or egg retrieval. Cryopreservation is also an alternative method when there is a risk of ovarian hyperstimulation syndrome (OHSS). In this case, all embryos are frozen and when the woman overcomes the risk they are defrosted, and embryo transfer is performed.
The embryo transfer of cryopreserved embryos to the uterus is scheduled so that proper endometrial preparation can be achieved. It can be done either in a natural cycle of the woman monitoring the ovulation or by creating the appropriate time period (implantation window) by administering some hormones.
This method is recommended in the following cases:
Mandatory absence of the spouse on the day of egg retrieval.
Scheduled chemotherapy, radiation therapy, or even testicular removal in cases of neoplastic disease, to cope with the risk of loss of the reproductive capacity of the man.
The progressive decline in sperm parameters.
After testicular biopsy, if there is an excess of sperm, so that the patient does not have to undergo new surgery.
When it is difficult to obtain the sample for psychological reasons or when it is taken by electrostimulation.
This method may be an alternative method for women who are going to undergo chemotherapy or radiotherapy. These treatments are significantly associated with subsequent ovarian failure.
In addition, women who do not intend to conceive in the coming years can cryopreserve their eggs to “protect” them over time. In these women ovarian stimulation and egg retrieval are done and then the mature eggs are frozen.
This method has not worked very well so far because these cells are very sensitive to temperature changes. However, scientific developments in this field are rapid and the survival and fertilisation rates of eggs after defrosting are constantly improving.
OVARIAN TISSUE CRYOPRESERVATION
Ovarian tissue cryopreservation is a promising method for women undergoing treatment for malignant diseases. In this method, a portion of the ovary is removed and after proper treatment is cryopreserved and stored for future use.
The options available for future use are as follows:
- isolation of immature ova from the follicles of the tissue, maturing them in the laboratory and then fertilizing them by the method of micro-fertilisation, so as to produce embryos.
- autologous tissue transplant to the woman either at the same site (orthotopic transplant), for the purpose of proper vascularization and re-operation, or at another site (heterotopic transplant), followed by stimulation, puncture egg retrieval and IVF,
- heterologous transplant to another woman (this method tends to be abandoned because it has many disadvantages). The results of this method are not always desirable and there are many difficulties. However, the progress made on this cryopreservation and transplant technique, particularly with regard to autologous orthotopic transplant, is impressive, giving many women hope.