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Cryopreservation of human embryos and its contribution to in vitro fertilization success rates

https://doi.org/10.1016/j.fertnstert.2014.05.027Get rights and content
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Cryopreservation of human embryos is now a routine procedure in assisted reproductive technologies laboratories. There is no consensus on the superiority of any protocol, and substantial differences exist among centers in day of embryo cryopreservation, freezing method, selection criteria for which embryos to freeze, method of embryo thawing, and endometrial preparation for transfer of frozen-thawed embryos. In the past decade, the number of frozen-thawed embryo transfer cycles per started in vitro fertilization (IVF) cycle increased steadily, and at the same time the percentage of frozen-thawed embryo transfers that resulted in live births increased. Currently, cryopreservation of human embryos is more important than ever for the cumulative pregnancy rate after IVF. Interestingly, success rates after frozen-thawed embryo transfer are now nearing the success rates of fresh embryo transfer. This supports the hypothesis of so called freeze-all strategies in IVF, in which all embryos are frozen and no fresh transfer is conducted, to optimize success rates. High-quality randomized controlled trials should be pursued to find out which cryopreservation protocol is best and whether the time has come to completely abandon fresh transfers.

Key Words

IVF
embryo cryopreservation
endometrial receptivity
slow freezing
vitrification
embryo transfer

Cited by (0)

K.M.W. has nothing to disclose. S.M. has nothing to disclose. S.R. has nothing to disclose.

Supported by the Netherlands Organization for Health Research and Development (grant 171101007) and the University of Amsterdam.