Copper-releasing intrauterine devices (IUDs) prevent pregnancy through multiple mechanisms. The SINGLE MOST IMPORTANT contraceptive mechanism of copper IUDs is:

• A Thickening of cervical mucus preventing sperm penetration
• B Spermicidal effect of copper ions on sperm motility and viability in the uterine cavity ✓
• C Inhibition of ovulation by local prostaglandin production
• D Decidualization failure causing implantation prevention as primary mechanism

Explanation

The primary mechanism of copper IUDs is the direct spermicidal and sperm-immobilizing effect of copper ions released continuously into the uterine cavity. Copper interferes with sperm capacitation, motility, and the acrosome reaction, significantly reducing the number of viable sperm reaching the fallopian tube. The local inflammatory reaction (sterile endometritis) and changes in tubal motility are secondary mechanisms. Copper IUDs do NOT significantly affect ovulation. Cervical mucus thickening is characteristic of progestogen-containing IUS (Mirena), not copper IUDs.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.