This volume contains the Proceedings of the Serono Symposium on Pre implantation Embryo Development, held in Newton, Massachusetts, in 1991. The idea for the symposium grew out of the 1989 Serono Symposium on Fertilization in Mammals* at which preimplantation development was the predominant suggestion for a follow-up topic. This was indeed a timely subject in view of the recent resurgence of interest in this funda mental phase of embryogenesis and its relevance to basic research and applied fertility studies in humans, food-producing animals, and endangered species. The symposium brought...

With a few notable exceptions, mammalian preimplantation embryos grown in vitro are likely to exhibit sub-optimal or retarded development. This may be manifested in different ways, depending on the species and on the stage(s) of embryonic development that are being examined. For example, bovine embryos often experience difficulty in cleaving under in vitro conditions, and usually cease development at about the 8-cell stage (Wright and Bondioli, 1981). The block to development is stage-dependent; embryos cultured for 24 hr from the I-cell stage are much more capable of developing into viable...