“…Administration of oestradiol at the time of norgestomet insertion has no effect on the ovulatory response (Wu et al, 1988;Bo et al, 1990Bo et al, , 1991, but results in fewer transferable embryos (Bo el al, 1990). When oestradiol injection was given at the same time as pFSH injection, rather than at norgestomet insertion, superovulation was markedly sup¬ pressed (Bo et al, 1991). Thus, we suggest that when progesterone or progestagens are used in conjunction with superovulation treatments, PGF2a rather than oestradiol should be the luteolytic agent of choice to avoid effects on dominant follicle turnover.…”