## Mechanism of Copper IUCDs **Key Point:** Copper-containing IUCDs work primarily through a spermicidal mechanism, NOT by preventing ovulation or implantation. ### Primary Mechanism 1. Copper ions are released from the device into the uterine cavity 2. These ions create a toxic environment for spermatozoa 3. Sperm motility is impaired and fertilization is prevented 4. Secondary effects include mild inflammatory response and altered endometrial environment ### Why NOT Ovulation or Implantation? - Copper IUCDs do NOT suppress ovulation (unlike hormonal methods) - They do NOT prevent implantation (this is a common misconception) - Ovulation occurs normally; the barrier is at fertilization **High-Yield:** The copper IUCD is a **non-hormonal, spermicidal contraceptive**. This is why it can be used in lactating women without affecting milk supply, and why it has minimal systemic side effects. **Clinical Pearl:** The spermicidal effect is dose-dependent — higher copper surface area (as in TCu 380A) provides better efficacy than lower-copper devices. [cite:Park 26e Ch 8]
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