Current aspects of blastocyst cryopreservation

Abstract

Cryopreservation of human gametes and embryos has become an essential part of assisted reproduction. Successful cryopreservation of human blastocysts is increasingly relevant as extended in-vitro culture of human embryos becomes more common, permitting routine use of blastocyst transfer in IVF programmes. This reduces the number of embryos transferred, thereby reducing multiple pregnancies and maximizing cumulative pregnancy rates per oocyte retrieval. The superiority of blastocyst freezing over earlier stage freezing in terms of implantation per thawed embryo transferred improves overall expectations for the cryopreservation programme. Therefore, a reliable procedure for the cryopreservation of blastocysts is needed because, after transfer, only a small number of supernumerary blastocysts are likely to be available for cryopreservation. Since the early 1980s, two common techniques have been used in cryopreservation: the conventional slow cooling method and the more recent rapid procedure known as vitrification. Vitrification has become an attractive alternative to slow freezing, since it appears to result in significantly higher survival and pregnancy rates. The aim of this review is to focus on the cryopreservation of human blastocysts using slow and rapid protocols and to assess the impact of the crypreservation protocol used on the survival, implantation and pregnancy rates.

The endometrial preparation for frozen-thawed euploid blastocyst transfer: a prospective randomized trial comparing clinical results from natural modified cycle and exogenous hormone stimulation with GnRH agonist

“…Moreover, some authors declare that cohort cryopreservation might convey an a priori greater chance of success [24]. At the same time, the development of vitrification and improved long-term in vitro culture systems lead to the better survival rate of frozen-thawed embryos, limiting cellular damage and enabling treated embryos to maintain the reproductive potential, comparable to fresh ones [43,50,51].…”

Whole sheep ovary cryopreservation: evaluation of a slow freezing protocol with dimethylsulphoxide

“…Whole ovary cryopreservation followed by transplantation with microvascular anastomosis may in the future become an effective oncofertility procedure There is a need for strict research protocols for whole ovary cryopreservation that test various freezing protocols and CPA, since most cryopreservation research in reproductive biology has been performed on tissue of small volumes such as oocytes [31], embryos [32] and blastocysts [33].…”

Live offspring from vitrified blastocysts derived from fresh and cryopreserved ovarian tissue grafts of adult mice

“…Embryo cryopreservation is a well-established protocol and many IVF clinics now reduce their multiple pregnancy rate by performing single embryo transfers and cryopreserving excess embryos (Youssry et al 2008). In humans, combination of oocyte and early stage of embryo cryopreservation have been used to produce healthy babies (Levi Setti et al 2005, Chen et al 2008.…”