Embryo cryopreservation and development: facts, questions and responsibility.

Four years ago, the results of an experimental study led us to conclude that in the mouse, cryopreservation of preimplantation embryo induced post-natal effects and thus could not be considered as neutral for the long-term development (Dulioust et al., 1995). This raised some concern in the scientific community and in the public about the safety of embryo cryopreservation in human assisted procreation. It has even been said that we had withdrawn our conclusions (Human Fertilisation and Embryology Authority, 1996); this was unfounded. Since then, only few studies have focused on this issue. Recently, a severe attack of our work was published (Testart, 1998). Here, we examine these criticisms and discuss the state of the art in the light of recent clinical and experimental studies.