The Copper-T 380A IUD has a stated effectiveness period of 10 years and a failure rate of 0.6 per 100 women-years (Pearl index). Which of the following is the main contraceptive mechanism of copper IUDs?

• A Creation of a physical barrier preventing sperm from reaching the fallopian tube
• B Copper ions cause sperm immobilisation, inhibit sperm motility/acrosome reaction, and are toxic to ova — primary pre-fertilization effect ✓
• C Endometrial inflammation prevents implantation as the primary mechanism
• D Alteration of tubal motility causing ectopic pregnancy prevention

Explanation

Copper IUDs exert their contraceptive effect primarily through copper ion toxicity to sperm: copper ions inhibit sperm motility, impair the acrosome reaction, and are directly toxic to ova, effectively preventing fertilization. The local endometrial sterile inflammatory reaction (leukocyte infiltration, altered endometrial biochemistry) serves as a secondary backup mechanism. The evidence shows that copper IUDs significantly reduce sperm reaching the tube and prevent fertilization in most cases, and that implantation prevention is a secondary, not primary, mechanism — an important distinction for contraceptive classification.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.