A 32-year-old woman with a history of deep vein thrombosis is counselled about contraceptive options. She wishes to use a progestin-only method. Which progestin-only contraceptive formulation is the most commonly used worldwide?

Explanation

## Most Common Progestin-Only Contraceptive: DMPA **Key Point:** Medroxyprogesterone acetate (DMPA, Depo-Provera) is the most widely used progestin-only injectable contraceptive globally, accounting for the majority of progestin-only contraceptive users worldwide. ### Why DMPA is Most Common **High-Yield:** DMPA has several advantages that explain its widespread use: - Long duration of action: 12 weeks (with 2-week grace period) - High efficacy: 99.7% with perfect use, 94% with typical use - Requires only 4 injections per year (IM or SC) - No user-dependent daily adherence required - Suitable for breastfeeding women - Particularly valuable in resource-limited settings - Cost-effective compared to other long-acting methods ### Comparison of Progestin-Only Contraceptives | Method | Duration | Frequency | Efficacy | Global Use | |---|---|---|---|---| | DMPA (IM/SC) | 12 weeks | 4×/year | 99.7% | **Most common** | | Norethisterone enantate | 8 weeks | 6×/year | 99.5% | Less common (mainly Africa) | | Levonorgestrel implant | 3 years | Single insertion | 99.95% | Growing use (LARCs) | | Levonorgestrel IUD | 5 years | Single insertion | 99.8% | Increasing in developed nations | | Progestin-only pill | 24 hours | Daily | 91–99% | Declining use | **Clinical Pearl:** DMPA is particularly valuable in this patient because she has a history of DVT, making combined hormonal contraceptives contraindicated (estrogen increases thrombotic risk). Progestin-only methods are safe in thrombophilia. ### Mechanism of Action 1. Suppresses LH surge → prevents ovulation (primary mechanism) 2. Thickens cervical mucus → reduces sperm penetration 3. Alters endometrium → hostile to implantation 4. Delays follicular development **Mnemonic:** **DMPA = Dependable, Monthly-interval, Progestin-only, Affordable** ### Side Effects and Considerations - Amenorrhea (develops in 40–50% by 12 months) — often viewed as an advantage - Delayed return to fertility (average 9–10 months after last injection) - Weight gain (average 2–3 kg over 5 years) - Bone mineral density loss (reversible; concern in adolescents) - No protection against STIs **Warning:** DMPA is contraindicated in undiagnosed vaginal bleeding, current breast cancer, and severe liver disease. It is safe in thrombophilia, making it ideal for this patient. [cite:KD Tripathi 8e Ch 61; WHO Medical Eligibility Criteria 2015]