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A comparative study of the contraceptive mechanism of the Cu-intrauterine device and the plastic-intrauterine device in rats.

After inserting the Cu-IUD and plastic-IUD into the horn of the uterus of rats, vaginal smears were daily observed for twelve estrus cycles, but no abnormal changes were noted. The female rats with the IUD were exposed to impregnation placing together with male rats. Neither the Cu-IUD nor the plastic-IUD affected copulation, and a complete contraceptive result was obtained in these rats. There were no significant differences in any effect examined between Cu-IUD and plastic-IUD groups. In order to investigate the influence of copper on the penetration of sperm, we placed the rats with the IUD under direct observation and then exposed them to natural copulation. By examining various sites of the reproductive organs 30 min after copulation, the hindrance of sperm migration by the Cu-IUD was confirmed.