Coculture of embryos on Vero cells and transfer of blastocysts in humans.

Preliminary results are presented concerning the first clinical application of cocultures of human embryos. In the experimental group, the embryos were cultured and transferred on day 5 post-insemination. Blastocyst formation was not dependent upon the stimulation regimen. Long term or ultrashort stimulation of the ovaries after gonadotrophin releasing hormone analogue gave 55-60% blastocyst formation. Serum was not necessary to obtain blastocysts. When the embryos were cocultured, we observed an increase in the implantation rates per embryo in the pregnant patients. However, a real increase in the pregnancy rate per transfer was observed in a population of patients who had had repeated failures of embryo transfer. This observation is discussed as possibly bypassing an effect of uterine motility, but the overall beneficial effect has to be assessed in a double blind randomized study. It is probable that improvements will not be observed for all the indications for in vitro fertilization.