VIABILITY OF PREIMPLANTATION EMBRYOS

Only about 10% of embryos obtained after in vitro fertilization (IVF) are able to implant after transfer in utero. Detecting the viable embryos is therefore the prerequisite condition to increase the overall efficiency of the technique. Zygote and embryo morphology is partly related to their viability. Indeed, fertilized oocytes with a timely fertilization and pronuclear growth, leading to embryos with equally sized blastomeres reaching at least the 4-cell stage about 42h after insemination, have the best chance of implanting. The metabolic approach, although requiring sensitive microassays, seems promising. Indeed, in a small series 100% of the pregnancies were predicted when the level of interleukin 1-α was >60 pg/ml and the suppressive level (antiproliferative activity using tumour cell lines) was >20% in the supernatant of transferred embryos. Lastly, invasive assessment of the chromosome status of embryos should allow us in future to discard severely abnormal embryos, thus increasing the success rate of IVF. © 1992 Baillière Tindall. All rights reserved.