There are certain cases in which you may have embryos that are not good enough to freeze--in other words, they're not going to survive being frozen and thawed--but they are not going to transfer either. Therefore, the idea that it's in the best interest of the patient to either transfer the embryos or freeze them is not actually the case. Yes, we transfer the fresh ones--one or two or three or whatever--and freeze some if we can, but there are still going to be other embryos that would otherwise be destroyed.
