Although the technique of oocyte vitrification has improved greatly in recent years, it still has some shortcomings and a percentage of cryopreserved oocytes may be lost upon devitrification. However, in the case of cryopreserved embryos, the possibility of losing them in devitrification is lower. Therefore, if we only look at the technical side, the answer to this question would be that it is better to cryopreserve embryos rather than oocytes.
But before making the decision to undergo IVF treatment in order to cryopreserve embryos, we must bear in mind that the objective of cryopreservation, in this situation that arises, is to postpone motherhood, and the woman or couple who wish to cryopreserve embryos must consider the possibility that their personal situation may change in the future.
In the case of couples, they must take into account that the embryos are affiliated to both parents, so that, in the event of a separation of the couple, the woman would not be able to dispose of them freely, having to obtain the consent of the man to use them, taking into account that the fruit of the gestation would be affiliated to him, that is to say, they would be his children.
In the case of single women who wish to preserve embryos generated with donated sperm, they should also consider the option of finding a partner in the future, in which case, unless they still maintain an adequate ovarian reserve, they would not be able to have biological children together.
In short, embryo cryopreservation is a technique with a better rate of results, but it is not free of future problems in the event that the woman's social conditions change when the time comes to use them.