The reasoning: block a step you understand
| Method | Mechanism | Typical‑use effectiveness (approx.) | Physiological notes |
|---|---|---|---|
| Combined hormonal (pill, patch, ring) | E suppresses FSH (no follicle selection); progestin suppresses LH surge; mucus thickening | ~91–93% (pill) | EE ↑ hepatic SHBG, clotting factors, angiotensinogen → VTE and BP effects; contraindicated in migraine with aura, smokers ≥ 35, < 6 weeks postpartum breastfeeding |
| Progestin‑only pill | mucus; ovulation suppression (desogestrel consistently) | ~91–93% | irregular bleeding; no oestrogen VTE risk |
| DMPA injection | ovulation suppression | ~94–96% | reversible bone density loss; delayed return of fertility |
| Implant (etonogestrel) | ovulation suppression | > 99% | LARC — most effective reversible |
| LNG‑IUS | local endometrial suppression, mucus | > 99% | reduces menstrual bleeding |
| Copper IUD | Cu²⁺ spermicidal inflammatory reaction | > 99% | may increase bleeding/pain; most effective emergency method (within 5 days) |
| Emergency oral | LNG (≤ 72 h) or ulipristal (PR modulator, ≤ 120 h) delay ovulation | — | ineffective once the LH surge has begun; not abortifacient |
| Male condom | barrier | ~87% | only method protecting against STIs |
| Vasectomy | interrupts vas | > 99% | needs post‑procedure semen test (residual sperm) |
| Tubal sterilisation | interrupts tube | > 99% | ectopic risk if failure |
| LAM | ↓ GnRH pulsatility | ~98% when all criteria met | conditional |