10. Human embryo cryopreservation and its effects on embryo morphology

Cryopreservation may have a variety of effects on embryo morphology, ranging from subtle damage on intracellular organelles, cytoplasm, or processes that can negatively affect normal cell development, to overtly blatant effects such as the lysis of one or more blastomeres. Many underlying factors can influence the outcome of cryopreservation, e.g. the quality of the oocyte or embryo itself will often determine the effects of the process on subsequent morphology. The type of freezing protocol used (slow-cooling or vitrification) and the concentration and type of cryoprotectant(s) will also have an effect on subsequent morphology. The goal of this chapter is to offer an insight into the question: how does cryopreservation affect subsequent embryo morphology? We address this question in three major sections: background, types of cryopreservation damage, and causes of damage.