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Contraception - Background information
How do copper intrauterine devices (IUDs) prevent pregnancy?
- The primary mode of action of copper intrauterine devices (IUDs) is via the toxic effects of copper on the ovum and sperm, preventing fertilization. In addition, alterations in the copper content of cervical mucus may inhibit penetration by sperm, and inflammatory reactions within the endometrium may prevent implantation, should the ovum be fertilized [Stanford and Mikolajczyk, 2002; FFPRHC, 2004a].
- Consequently, the copper IUD can work immediately after insertion.
- A judicial review ruled that pregnancy begins, not at fertilization, but at implantation; thus the copper IUD is not legally considered an abortifacient [DH, 2002].
- For information on using the copper IUD for emergency contraception, see the CKS topic on Contraception - emergency.
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