Emergency Contraception Timing After Unprotected Intercourse
Emergency contraception must be used within 5 days (120 hours) of unprotected intercourse, with the copper IUD being the most effective option throughout this entire window, followed by ulipristal acetate (ella), while levonorgestrel (Plan B) is most effective within the first 72 hours. 1, 2
Method-Specific Deadlines and Effectiveness
Copper IUD (Most Effective)
- Can be inserted up to 5 days (120 hours) after unprotected intercourse with the highest efficacy of all emergency contraception methods (<1% failure rate) 2, 3
- Maintains consistent effectiveness throughout the entire 5-day window 2
- Provides ongoing long-term contraception after insertion 1, 4
Ulipristal Acetate (Ella) - 30mg Single Dose
- Approved for use up to 5 days (120 hours) after unprotected intercourse 1, 5
- Maintains effectiveness throughout the full 120-hour window, with no significant differences in pregnancy rates across the five 24-hour intervals 5
- More effective than levonorgestrel after 72 hours and should be the preferred oral option between 72-120 hours 1, 3
- Particularly more effective in women who are overweight or obese (>165 lbs or BMI >30) 1, 3, 6
- Observed pregnancy rate of 1.9% when taken within 72 hours, and as low as 1.3% when taken between 96-120 hours 2, 5
Levonorgestrel (Plan B) - 1.5mg Single Dose
- FDA-approved for use up to 72 hours (3 days) after unprotected intercourse, but can be taken up to 120 hours with reduced effectiveness 7, 4
- Most effective within the first 72 hours, with treatment reducing pregnancy risk by at least 75% 7, 8
- Effectiveness decreases significantly after 72 hours, with pregnancy rates increasing at 4-5 days 1, 3, 7
- Should be taken as soon as possible after unprotected intercourse to maximize effectiveness 7, 9
- May be less effective in women with higher body weight (>165 lbs or BMI >30) 3, 6
Clinical Decision Algorithm
Within 0-72 hours:
- Normal weight women: Levonorgestrel 1.5mg OR ulipristal acetate 30mg 3, 7
- Women >165 lbs or BMI >30: Ulipristal acetate 30mg preferred over levonorgestrel 3, 6
- Copper IUD for maximum efficacy regardless of weight 2, 3
Between 72-120 hours:
- Ulipristal acetate 30mg is the only effective oral option at this timepoint 2, 3
- Levonorgestrel is NOT recommended due to significantly reduced effectiveness 2, 3
- Copper IUD remains highly effective 2, 3
Beyond 120 hours:
Critical Post-Treatment Instructions
After Levonorgestrel Use:
- Resume regular contraception immediately 7
- Use barrier method or abstain for 7 consecutive days after restarting hormonal contraception 2, 3
After Ulipristal Acetate Use:
- Any contraceptive method can be started immediately 2, 7
- Barrier contraception or abstinence required for 14 consecutive days (or until next menses) 2, 3
If Vomiting Occurs:
- If vomiting occurs within 3 hours of taking emergency contraception, another dose should be taken as soon as possible 7
Important Clinical Considerations
- No pregnancy test or physical exam is required before prescribing emergency contraception 10
- Emergency contraception does not harm an established pregnancy and does not cause abortion 6, 9
- Advance provision of emergency contraception is supported and may increase timely use 1, 2, 7
- Women already on combined oral contraceptives or depot medroxyprogesterone acetate can and should use emergency contraception if unprotected intercourse has occurred 2