Blastocyst transfer after aseptic vitrification of zygotes: an approach to overcome an impaired uterine environment

In some IVF cycles, no fresh embryo transfer in the stimulated cycle is advisable. The cryopreservation of zygotes and the transfer of blastocysts in a cryo-embryo transfer is an option to circumvent an inadequate uterine environment due to risk of ovarian hyperstimulation syndrome, inappropriate endometrium build up, endometrial polyps or uterine myomas. For this strategy, highly secure and safe cryopreservation protocols are advisable. This study describes a protocol for aseptic vitrification of zygotes that results in high survival rates and minimizes the potential risk of contamination in liquid nitrogen during cooling and long-term storage. In mouse zygotes, there was no difference in efficiency as compared with a conventional open vitrification system. In IVF patients, aseptically vitrified zygotes showed no difference in blastocyst formation rate as compared with sibling zygotes kept in fresh culture. A clinical study comprising 173 cryo-cycles with a transfer of blastocysts originating from vitrified zygotes showed an ongoing pregnancy rate of 40.9%. The live birth rate per patient was 36.8%. A combination of good clinical results and increased safety conditions due to aseptic vitrification encourages the use of cryo-embryo transfer for patients with a suboptimal uterine environment in a fresh cycle

Closed carrier device: A reality to vitrify oocytes and embryos in aseptic conditions

Vitrification with the use of ‘‘Open’’ carrier devices (Cryoloop, cryotop, cryoleaf, Vitriplug) which allowed the contact with liquid nitrogen has become a more popular way to achieve cooling rate superior to 20.000 °C/min. Even though the question of contamination with liquid nitrogen during ultra-rapid cooling and storage remain debatable with the use of ‘‘open’’ devices, it is important to revise the carrier system in a way, which minimizes the risk of contamination. According to the EU tissues and cells directive, it is advisable that the cooling and storage should be carried out in embryo carrier devices ensuring complete separation of the embryos from liquid nitrogen in a way, which minimizes the risk of contamination. The consequence of a reduction in the cooling rate resulting from the heat-insulating barrier of aseptic devices has to be counteracted by gradually increasing intracellular concentrations of cryoprotectants without inducing a toxic effect. We developed an aseptic vitrification method of vitrification for MII oocytes and embryos at different stage of development using the ‘‘VitriSafe’’ as ‘‘closed’’ carrier device

Chapter 13: Adaptation of a Universal Procedure for Cryopreservation of Different Developmental Stages: Is it Conceivable?

A RENEWED INTEREST IN CRYOPRESERVATION: WHY? It is now well recognized that the proportion of births following transfer of cryopreserved gametes or embryos will increase dramatically. Several reasons may explain this rising interest for embryo transfer (ET) after cryopreservation. The improvement of in vitro culture technique enables gaining better quality embryos associated with the policy of single embryo transfer (SET) results in the increasing proportion of supernumerary embryos cryopreserved at different stages of development. Moreover, with the increased efficiency of the cryopreservation technique such as vitrification, there is now a tendency to shift from fresh ET to cryopreserved ET in artificial or natural cycles. This attitude is relevant especially when the progesterone level before oocyte pick-up is above a physiological limiting value, a not optimal thickness of the endometrium or when embryos are originated from an in vitro maturation cycle. Cryopreserved ET is also an opportunity, when fresh ET cycles are cancelled because of hyperstimulation. With the introduction of vitrification, there is also an emergent change in the general attitude towards oocyte cryopreservation offering available solution, for example, in the field of preservation of fertility, ovarian hyperstimulation syndrome, poor responder, absence of sperm at the time of oocyte pick-up, cryo-banking for egg donation program or for social reason and finally to overcome ethical concerns and legal restrictions