Incidence of polyspermy in mouse eggs fertilized in vivo and in vitro after administration of progesterone and oestradiol.

Female mice, induced to superovulate, were injected subcutaneously with progesterone or oestradiol near the time when hCG was given. The incidence of polyspermy in first-cleavage embryos following mating or in-vitro fertilization was then determined. There were no detectable differences in the incidence or degree of polyspermy between treated and control in either the in-vitro or in-vivo groups, although the mean incidence of polyspermy was higher in vitro than in vivo. Furthermore, there was no detectable acceleration of egg transport after administration of either hormone.