Chapter 9 Slow Freezing and Thawing of Human Cleavage Stage Embryos

The ability to store human embryos in a viable state at very low temperatures has been critical to the evolution of responsible practice in clinical Assisted Reproductive Technology (ART). It has encouraged a reduction in the frequency of simultaneous multiple embryo transfer and thereby reduced the risks associated with multiple pregnancy while maintaining high cumulative pregnancy rates from single oocyte collection cycles. In this chapter, we describe a simple slow freezing procedure for human early cleavage stage embryos that results in a high proportion of post-thaw embryos surviving and retaining their implantation potential.