Emergency contraception: real-world effectiveness
Updated: 2026-07-08 Β· Not medical advice
Summary
Emergency contraception (EC) reduces pregnancy risk after unprotected intercourse but does not eliminate it. Effectiveness depends on timing, body weight, and which product is used.
Key points
- Levonorgestrel pills (e.g., Plan Bβtype) work best within 72 hours; efficacy declines with delay and higher body weight.
- Ulipristal acetate may remain more effective closer to 120 hours in some studies.
- Copper IUD used as EC is highly effective when placed promptly by a clinician.
- EC does not end an established pregnancy; it prevents or delays ovulation/fertilization.
What research suggests
WHO and national guidelines emphasize as soon as possible administration. Typical-use pregnancy rates after EC remain non-zero; ongoing contraception is recommended.
Limitations
Vomiting within hours of dosing, drug interactions, and repeated EC use in one cycle require medical advice.