Copper T IUD: Mechanism of Action and Disadvantages
Mechanism of Action
The Copper T IUD works primarily by preventing fertilization through copper ion toxicity to sperm, not by causing abortion. The copper ions create a hostile environment in the genital tract that impairs sperm function before fertilization can occur 1, 2, 3.
Primary Contraceptive Mechanisms:
Spermicidal effect: Copper ions released from the device reach concentrations in uterine and tubal fluids that are directly toxic to sperm, impairing their motility, viability, and fertilizing capacity 2, 3, 4.
Prevention of fertilization: The copper ions affect sperm function throughout the entire genital tract, not just the uterus, significantly decreasing the rate of fertilization before any embryo can form 2, 3.
Foreign body inflammatory reaction: All IUDs induce a local inflammatory response in the endometrium, with cellular and humoral components that further impair gamete function 2, 3.
Interference with sperm-egg interaction: Even at low concentrations similar to those released from IUDs, copper affects the fertilizing capacity of human gametes and interferes with sperm-oocyte interaction 4.
Secondary Mechanism (If Fertilization Occurs):
Post-fertilization effect: If fertilization does occur (which is rare), copper ions can influence the endometrium to prevent implantation, though this is not the primary mechanism 1, 2.
Emergency contraception: When used within 5 days of unprotected intercourse, the Copper T IUD is the most effective emergency contraceptive method available, working through both prevention of fertilization and, if needed, prevention of implantation 1.
Disadvantages
Lack of STI Protection:
- No protection against sexually transmitted infections: The Copper T IUD does not protect against STIs or HIV, and condoms must be used concurrently if there is any risk of infection 5.
Infection Risks:
Increased risk of pelvic inflammatory disease during insertion: Among women with chlamydial infection or gonorrhea, there is a potential increased risk for PID with IUD insertion, making it a Category 3 condition (risks usually outweigh benefits) in high-risk STI situations 5.
Risk limited to insertion period: The risk of pelvic infection occurs primarily during the first 20-21 days after insertion, not during long-term use 5.
Contraindications and High-Risk Situations:
Absolute contraindication in pregnancy: IUD use during pregnancy carries risk for serious pelvic infection and septic spontaneous abortion, making it a Category 4 condition (unacceptable health risk) 5.
Should be avoided in high-risk STI situations: In cases of rape or sexual assault with high risk for STI, insertion should generally be avoided (Category 3) unless the woman can be screened and treated first 5.
Clinical Pitfalls to Avoid:
Screen for STIs on day of insertion: Unless the patient is at very high risk (e.g., partner with known gonorrhea), screening for gonorrhea and chlamydia can be performed on the day of insertion, with treatment provided afterward if needed without removing the device 5.
No backup contraception needed: Unlike hormonal methods, the Copper T IUD requires no backup contraception after insertion, as it is immediately effective 5.
Higher expulsion rates in younger women: Limited data suggest that expulsion (occurring in fewer than 5% of women) may occur more frequently in adolescents and younger nulliparous women 5.