[Factors affecting the results of in vitro fertilization. V. Co-culture of embryos]

Pronuclear stage embryos were divided into two groups and cultivated in i) M-199 or in ii) M-199 on a monolayer of Vero cells for 48, 60 or 72 hours respectively. Under the standard conditions (i) no significant differences in pregnancy rate (PR) were found (48 and 60 h; PR 20.14% and 20.39%). The prolonged culture influenced negatively embryo development (data not shown). On the other hand, clear differences were found after the culture on the Vero cell monolayer. Embryos cultured for 48 h gave considerably higher PR compared for 60 h (24.34% and 13.04% resp.). The embryos developing successfully after 72 h produced the highest PR (33.33%). The implantation rate is also significantly higher (19.1% P < 0.001). Although it is quite clear that our culture conditions are not yet ideal, it is evident that embryos which are able to develop normally for three days in vitro are much better equipped for further development.