The effect of varying inseminating sperm concentration in male factor and non-male factor infertility during in vitro fertilization.

Objective: To assess the effect of varying inseminating sperm concentrations on fertilization rates and polyspermy in human in vitro fertilization (IVF).

Subjects and methods: Eighty-six couples who completed 107 consecutive IVF cycles were assigned to one of three groups according to the results of their semen analysis (SA), sperm penetration assay (SPA), and titers of antisperm antibodies (ASA). Group 1 (non-male factor) had normal results for SA, SPA and ASA; group 2 had one abnormal result; and group 3 had two or more abnormal results. Inseminating concentrations of 50,000, 250,000, or 500,000 progressively motile sperm/oocyte were prospectively assigned to groups 1, 2 and 3, respectively.

Main outcome measures: Incidence of polyspermy and fertilization rates.

Results: A total of 992 oocytes were available for analysis. The fertilization rate of 61% for non-male factor patient (group 1) was significantly higher than for male-factor patients [group 2 (48%) and group 3 (43%; P < .01)]. The incidence of polyspermy was 3.3%, 5.5%, and 0% for groups 1, 2 and 3, respectively, and did not differ significantly between the non-male factor and male factor groups (P = .16). Polyspermic fertilization was increased in both mature (4.1%) and postmature (5.7%) as compared to immature oocytes (1.4%; P < .05).

Conclusion: In male factor infertile couples, increasing the inseminating concentration to 250,000 or 500,000 motile sperm/oocyte does not result in an increase in the incidence of polyspermy but does not improve fertilization rates.