Utilization of embryos from previously superovulated mice in an in vivo fertilization system.

When stringent quality control has been an integral part of an IVF-ET program, there has been an indication of more consistent pregnancy rates (8,9). We were therefore hesitant to introduce any variables, such as reutilizing previously stimulated mice, which might affect our quality-control system. However, from the results of our study there appeared to be no significant difference in the number of two-cell embryos retrieved between the control and the experimental groups. No difference was noted in the percentages of embryos reaching beta blastocyst. Although not significant, there did appear to be a decrease in mating when mice were stimulated more than once.