Interdependent influence of follicular fluid oestradiol concentration and motility characteristics of spermatozoa on in-vitro fertilization results.

Methods are presented for an objective assessment of the quality of both gametes in an in-vitro fertilization programme. The concentrations of oestradiol and progesterone in follicles whose oocytes did or did not fertilize, were measured and assessed as potential markers of oocyte maturity. There was no difference in the mean concentrations of either steroid in follicular fluid of fertilized and unfertilized oocytes. However, a highly significant inverse correlation was observed between the oestradiol concentration in follicles of oocytes becoming fertilized and the number of spermatozoa added for fertilization (P less than 0.001). Follicular fluid concentrations of progesterone did not correlate with the number of inseminated spermatozoa. The correlation between follicular oestradiol concentrations and the number of spermatozoa needed for fertilization was then used to identify movement characteristics of spermatozoa in the culture medium which were relevant for fertilization. Sufficient numbers of spermatozoa having specific values of head cross frequency, lateral head displacement, linearity and curvilinear velocity were critical for the occurrence of fertilization in vitro.