The aim of this work was to evaluate prolongation of cultivation time of human embryos. The prolongation above the standard limit was implemented (1) by coculture of embryos on a monolayer of human epithelial cells and (2) by using a synthetic medium.
Material and methods: Ovarian stimulation, oocyte recovery, insemination and cultivation up to the pronuclear stage were done in our centre in the usual way. Group I: 104 women, prolonged culture by the coculture method. The zygotes were placed on the monolayer and cultivated for an other 24 or 48 hours. Group II: 249 women, prolonged culture in a synthetic medium. The zygotes were cultivated up to the 2- to 4-cell stage in standard IVF medium, and then put into M3 medium for the next 24 or 48 hours. A transfer of a maximum of 4 embryos was done.
Results: In group I in 104 women from 341 zygotes 181 embryos (53.1%) reached the eight- and more than eight-cell stage, and 76 transfers were done. 15 pregnancies were achieved (19.4% pregnancy rate). In group II in 249 patients from 672 embryos 49.7% of them reached 8- and more than 8-cell stage. 51 pregnancies were achieved (22.6 pregnancy rate). In the control group of 250 IVF after 48 hours cultivation 165 transfers (66.0%) were done, and 16.4% pregnancies were achieved, i.e. 6.2% less compared to synthetic medium and 3.3% less than in cocultivation.
Conclusion: There is evidence of better IVF/ET results in case of prolonged culture time. The experience in our centre has shown the need of reevaluation of the coculture method. The exacting character of its preparation and manipulation will have to be replaced by synthetic media in spite of their high price.