Copper content in cervical mucus of women wearing plain and copper-bearing spring coils

To test the hypothesis that the copper in copper-bearing intrauterine devices (IUDs) and its reaction with cervical mucus constitute the agent in preventing conception, the copper content of 300 samples of cervical mucus, 150 each from women wearing plain Spring Coil IUDs and those wearing Spring Coils containing 500 mg of copper, was determined at 3, 6 and 12 months after IUD insertion. Stoner and Dasler's modified spectrophotometric micromethod (Clin Chem 10:845, 1964) was used to quantify the copper content of the cervical mucus. Analysis showed no significant change in the copper content of the cervical mucus of women wearing plain Spring Coils compared to that of women not wearing IUDs; however, the amount of copper in the cervical mucus of women wearing copper-bearing Spring Coils was 5--6 times greater at midcycle 3, 6 and 12 months after insertion. Thus, we conclude that there is an important biologic basis for assuming that copper-bearing Spring Coils can inhibit sperm penetration through the cervical mucus and that they can initiate contraceptive activity at the cervical level.