Abstract
Cryopreservation of human gametes, embryos and blastocysts has become an integral part of assisted reproduction. This approach may have several advantages for infertile patients. It provides an opportunity to limit the numbers of embryos transferred while supernumerary embryos will be used in subsequent treatment cycles, thereby increasing the cumulative pregnancy rate. Furthermore, the potential risk of hyperstimulation syndrome can be reduced. In addition, storage of embryos from a cycle allows the patient to space the timing of sibling pregnancies and improve their potential of achieving a pregnancy at an advanced maternal age. Therefore, a reliable procedure for the cryopreservation of supernumerary embryos is needed. 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. The latter needs a much higher concentration of cryoprotectants and faster cooling rates. Vitrification is qualified to be the future of cryopreservation procedure owing to increased survival and success rates over the last years. The aim of this review is to assess the outcomes of different methods of cryopreservation performed on human embryos and to evaluate whether vitrification nowadays is ready to replace slow freezing.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.