A 28-year-old nulliparous woman attends the family planning clinic seeking long-acting reversible contraception. She has no contraindications to hormonal methods and desires a method with minimal systemic hormone exposure. She is counselled about the copper T380A IUD and the levonorgestrel-releasing IUS (LNG-IUS). Which of the following statements regarding the mechanism of action of these two devices is correct?

Explanation

## Mechanism of Action: Copper T380A vs LNG-IUS ### Copper T380A (Non-hormonal IUCD) **Key Point:** Copper T380A works through multiple local mechanisms: 1. **Spermicidal effect** — copper ions are directly toxic to sperm, reducing motility and fertilizing capacity 2. **Endometrial inflammation** — sterile inflammatory response impairs implantation 3. **Altered tubal motility** — affects sperm and ovum transport 4. **Minimal systemic absorption** — works primarily at the local level ### Levonorgestrel-Releasing IUS (LNG-IUS) **Key Point:** LNG-IUS combines local and systemic effects: 1. **Cervical mucus thickening** — high local progestin concentration increases mucus viscosity 2. **Endometrial suppression** — causes endometrial atrophy and decidualization, preventing implantation 3. **Partial ovulation inhibition** — approximately 20–40% of cycles remain ovulatory due to local rather than systemic hormone levels 4. **Tubal effects** — alters tubal secretions and motility ### Comparative Table | Feature | Copper T380A | LNG-IUS | | --- | --- | --- | | **Primary mechanism** | Spermicidal + endometrial inflammation | Cervical mucus + endometrial atrophy | | **Ovulation suppression** | No | Partial (20–40% cycles ovulatory) | | **Systemic hormone** | Minimal/none | Low but measurable | | **Efficacy (Pearl Index)** | 0.8 per 100 woman-years | 0.2 per 100 woman-years | | **Effect on menses** | Increased bleeding (20–30%) | Decreased/amenorrhea (60–70%) | | **Ectopic pregnancy risk** | Lower absolute risk (works before fertilization) | Lower relative risk (fewer pregnancies overall) | **High-Yield:** Copper T380A prevents pregnancy *before* fertilization (spermicidal), while LNG-IUS prevents implantation *after* fertilization (endometrial effect). Neither reliably prevents ectopic pregnancy, but absolute risk is lower with copper T380A because fewer pregnancies occur overall. **Clinical Pearl:** LNG-IUS is preferred in women with heavy menstrual bleeding (HMB) because it reduces menstrual flow by 60–70%, whereas copper T380A may worsen HMB by 20–30%. ### Why Copper T380A is Suitable for Nulliparous Women **Key Point:** Despite older teaching, copper IUCDs are now recommended for nulliparous women by WHO and ACOG (2012 onwards). Nulliparity is *not* a contraindication. Copper T380A offers: - No systemic hormone exposure - Excellent efficacy (>99%) - Rapid return to fertility - No impact on lactation [cite:Park 26e Ch 8]