Immobilization of sperm by condoms and their components

Condoms and other rubber products immobilize sperm, but the mechanism is unknown. Sperm motility and eosin Y exclusion were measured following exposure of samples of semen to latex condoms of various types. Sperm motility was markedly reduced by exposure to all latex condoms, but eosin Y exclusion was unchanged. While there appeared to be some variability between semen samples and in time to complete immobilization of all sperm, condoms from one batch were similar. The immobilizing effect was not altered by prewashing the condom with buffer, chelating agent or acid. After immobilization, motility was not recovered by sperm washed in buffer, mixed with normal mid-cycle cervical mucus, or exposed to caffeine or adenosine triphosphate after demembranation with detergent. Studies with components of condoms indicated that raw latex and zinc dimethyl- and dibutyl-dithiocarbamate accelerators immobilized sperm within 30 min. In contrast, silicone rubber had no effect on sperm motility for up to 4 h. Enhancement of the sperm immobilizing effect might improve the contraceptive efficacy of condoms, while a useful non-toxic sperm collecting device for semen analysis, artificial insemination or in vitro fertilisation might be developed by omitting the toxic components from the rubber.