**5. Blastocyst stage**

Vitrification of human blastocysts using different carriers shows survival rates of 70% to 90%, with clinical pregnancy rates of 37% to 53% and implantation rates of 20% to 30% ((Yokota *et al*., 2000, 2001; Reed *et al*., 2002; Mukaida *et al*., 2001; 2003; Hiraoka *et al*., 2004; Vanderzwalmen *et al*., 2002; 2003; Huang *et al.,* 2005; Liebermann & Tucker, 2006; Liebermann, 2009, 2011).
