That decision would be made primarily by the embryologist, who studies the quality of an embryo in a laboratory to determine whether it would be able to survive being frozen and thawed. The embryologist, in consultation with the clinician and the couple whose embryo it is, will then make a decision as to whether that embryo should be frozen, if that's what they really want, even though they're aware that it might not survive being frozen and thawed, or whether it should be destroyed or be considered for research.
On December 12th, 2006. See this statement in context.