Slow Freezing of Embryos

  • Liesl Nel-Themaat
  • Ching-Chien Chang
  • Thomas Elliott
  • Diana P. Bernal
  • Graham Wright
  • Zsolt Peter Nagy


Cryopreservation of embryos has become an integral part of infertility treatment worldwide. Improvement of embryo culture systems, a vast increase in the use of preimplantation genetic diagnosis, combined with data indicating benefits of freeze-only cycles over fresh transfers have ensured that embryo cryopreservation will be included during the treatment of the majority of IVF patients.

The current chapter describes the slow freezing of human embryos as used in a clinical setting. Although the use of slow freezing for cryopreservation of embryos has been declining over the past several years, most programs still have to thaw slow frozen embryos from time to time, and some still use it as their standard procedure for cryopreservation. Since the thawing procedure is closely related to the freezing procedure used, principle knowledge of not only embryo thawing but also freezing is still essential for clinical embryology labs. In this chapter, we first embark on a voyage through time, reviewing the history of how the field of cryobiology, as we know it today, evolved. Then, the principles of embryo cryobiology, including mechanisms of freeze/thaw damage, components of the procedure and factors that determine success rates are discussed. We also look at slow freezing of embryos at different developmental stages. Subsequently, some ancillary procedures such as lysed cell removal and assisted hatching are discussed before comparing slow freezing with vitrification. Finally, some legal and ethical considerations of cryopreservation in general are discussed before touching on the future of slow freezing in clinical embryology. The authors conclude that most clinical IVF programs will continue to benefit from the knowledge of slow freezing and thawing procedures.


Slow freezing Cryopreservation Embryo Thawing Cryoprotectants 


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Liesl Nel-Themaat
    • 1
  • Ching-Chien Chang
    • 2
  • Thomas Elliott
    • 2
  • Diana P. Bernal
    • 3
  • Graham Wright
    • 4
  • Zsolt Peter Nagy
    • 2
  1. 1.Department of Advanced Reproductive MedicineUniversity of Colorado DenverStapletonUSA
  2. 2.Reproductive Biology Associates – PreludeAtlantaUSA
  3. 3.Biotech INCAlpharettaUSA
  4. 4.Reproductive Biology AssociatesAtlantaUSA

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